fix(bulk-edit): cycle-3 polish — Felix C2/C3/C4/C5 + Sara coverage gaps

Felix C2 — `BatchMetadataRequest` controller now uses `@Valid` so future
@Size/etc. annotations on the record actually fire.

Felix C3 — Auto-clear `$effect` in `+layout.svelte` reads
`bulkSelectionStore.size` inside `untrack()` so the effect only re-fires on
route change, not on every checkbox toggle.

Felix C4 — `BulkDocumentEditLayout` edit-mode hydration loop now lives
inside `onMount` (not at top-level script) so the SvelteMap mutation is
unambiguously tied to instance lifecycle, matching the pattern used by
`WhoWhenSection`/`DescriptionSection` after the cycle-2 fix.

Felix C5 — Replaced fully-qualified `java.util.LinkedHashSet` in
`DocumentController` with a top-of-file import.

Sara coverage — six new spec files / blocks pin the cycle-1 and cycle-2
behaviours that were previously untested:
 - `WhoWhenSection.svelte.spec.ts` — onMount seeding from initialDateIso /
   initialLocation; doesn't stomp parent-bound dateIso; hideDate / editMode
   branch
 - `DescriptionSection.svelte.spec.ts` — onMount seeding from initialTitle /
   initialDocumentLocation; doesn't stomp parent-bound values; archive-box /
   archive-folder fields visible only in editMode
 - `BulkSelectionBar.svelte.spec.ts` — Esc-scope guard tests for `<dialog>`
   open and `aria-expanded` popover present
 - `BulkDocumentEditLayout.svelte.spec.ts` — topbar reads
   "Massenbearbeitung" + "werden bearbeitet" in edit mode (not the
   upload-flavoured "hochladen"/"werden erstellt" copy)
 - `DocumentControllerTest.patchBulk_returns400_whenArchiveBoxExceeds255Chars`
   — pins the @Size validator on archiveBox via the @Valid wiring

Refs #225, PR #331

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -47,6 +47,26 @@ jobs:
           name: unit-test-screenshots
           path: frontend/test-results/screenshots/
 
+  # ─── OCR Service Unit Tests ───────────────────────────────────────────────────
+  # Only spell_check.py, test_confidence.py, test_sender_registry.py — no ML stack required.
+  ocr-tests:
+    name: OCR Service Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install test dependencies
+        run: pip install "pyspellchecker==0.9.0" pytest pytest-asyncio
+        working-directory: ocr-service
+
+      - name: Run OCR unit tests (no ML stack required)
+        run: python -m pytest test_spell_check.py test_confidence.py test_sender_registry.py -v
+        working-directory: ocr-service
+
   # ─── Backend Unit & Slice Tests ───────────────────────────────────────────────
   # Pure Mockito + WebMvcTest — no DB or S3 needed.
   backend-unit-tests:

.gitignore

@@ -11,4 +11,5 @@ gitea/
 scripts/large-data.sql
 
 .vitest-attachments
-**/test-results/
+**/test-results/
+.worktrees/

CLAUDE.md

@@ -311,13 +311,15 @@ Save bar pattern — use **sticky full-bleed** for long forms (edit document), *
 <div class="mt-4 flex items-center justify-between rounded-sm border border-brand-sand bg-white px-6 py-4 shadow-sm">
 ```
 
-Back link pattern:
+Back button pattern — use the shared `<BackButton>` component from `$lib/components/BackButton.svelte`:
 ```svelte
-<a href="/persons" class="inline-flex items-center text-xs font-bold uppercase tracking-widest text-gray-500 hover:text-brand-navy transition-colors group mb-4">
-    <svg class="w-4 h-4 mr-2 transform group-hover:-translate-x-1 transition-transform" .../>
-    Zurück zur Übersicht
-</a>
+<script lang="ts">
+    import BackButton from '$lib/components/BackButton.svelte';
+</script>
+
+<BackButton />
 ```
+The component calls `history.back()` so the user returns to wherever they came from. Label is always "Zurück" (no contextual suffix — destination is unknown). Touch target ≥ 44px and focus ring are built in. Do not use a static `<a href>` for back navigation.
 
 Subtle action link (e.g. "new document/person"):
 ```svelte

backend/pom.xml

@@ -103,6 +103,11 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-webmvc-test</artifactId>
 			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.awaitility</groupId>
+			<artifactId>awaitility</artifactId>
+			<scope>test</scope>
 		</dependency>
 				<!-- Excel Bearbeitung (Apache POI) -->
 		<dependency>
@@ -146,6 +151,12 @@
 			<artifactId>flyway-database-postgresql</artifactId>
 		</dependency>
 
+		<!-- Caffeine cache for in-memory rate limiting -->
+		<dependency>
+			<groupId>com.github.ben-manes.caffeine</groupId>
+			<artifactId>caffeine</artifactId>
+		</dependency>
+
 		<!-- OpenAPI / Swagger UI — enabled only in the dev Spring profile -->
 		<dependency>
 			<groupId>org.springdoc</groupId>
@@ -153,12 +164,19 @@
 			<version>3.0.2</version>
 		</dependency>
 
-		<!-- PDF rendering for training data export -->
+		<!-- PDF rendering for training data export and thumbnail generation -->
 		<dependency>
 			<groupId>org.apache.pdfbox</groupId>
 			<artifactId>pdfbox</artifactId>
 			<version>3.0.4</version>
 		</dependency>
+
+		<!-- TIFF decoding plugin for ImageIO (thumbnail generation from scanned TIFFs) -->
+		<dependency>
+			<groupId>com.twelvemonkeys.imageio</groupId>
+			<artifactId>imageio-tiff</artifactId>
+			<version>3.12.0</version>
+		</dependency>
 	</dependencies>
 
 

backend/src/main/java/org/raddatz/familienarchiv/audit/ActivityActorDTO.java

@@ -0,0 +1,10 @@
+package org.raddatz.familienarchiv.audit;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.annotation.Nullable;
+
+public record ActivityActorDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String initials,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String color,
+        @Nullable String name
+) {}

backend/src/main/java/org/raddatz/familienarchiv/audit/ActivityFeedRow.java

@@ -0,0 +1,20 @@
+package org.raddatz.familienarchiv.audit;
+
+import java.time.Instant;
+import java.util.UUID;
+
+public interface ActivityFeedRow {
+    String getKind();
+    UUID getActorId();
+    String getActorInitials();
+    String getActorColor();
+    String getActorName();
+    UUID getDocumentId();
+    Instant getHappenedAt();
+    boolean isYouMentioned();
+    boolean isYouParticipated();
+    int getCount();
+    Instant getHappenedAtUntil();
+    /** Present only for COMMENT_ADDED and MENTION_CREATED — null otherwise. */
+    UUID getCommentId();
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditKind.java

@@ -0,0 +1,35 @@
+package org.raddatz.familienarchiv.audit;
+
+import java.util.Set;
+
+public enum AuditKind {
+
+    /** Payload: none */
+    FILE_UPLOADED,
+
+    /** Payload: {@code {"oldStatus": "UPLOADED", "newStatus": "TRANSCRIBED"}} */
+    STATUS_CHANGED,
+
+    /** Payload: none */
+    METADATA_UPDATED,
+
+    /** Payload: {@code {"pageNumber": 3}} */
+    TEXT_SAVED,
+
+    /** Payload: none */
+    BLOCK_REVIEWED,
+
+    /** Payload: {@code {"pageNumber": 3}} */
+    ANNOTATION_CREATED,
+
+    /** Payload: {@code {"commentId": "uuid"}} */
+    COMMENT_ADDED,
+
+    /** Payload: {@code {"commentId": "uuid", "mentionedUserId": "uuid"}} */
+    MENTION_CREATED;
+
+    public static final Set<AuditKind> ROLLUP_ELIGIBLE = Set.of(
+            TEXT_SAVED, FILE_UPLOADED, ANNOTATION_CREATED,
+            BLOCK_REVIEWED, COMMENT_ADDED, MENTION_CREATED
+    );
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditLog.java

@@ -0,0 +1,46 @@
+package org.raddatz.familienarchiv.audit;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.persistence.*;
+import lombok.*;
+import org.hibernate.annotations.CreationTimestamp;
+import org.hibernate.annotations.JdbcTypeCode;
+import org.hibernate.type.SqlTypes;
+
+import java.time.OffsetDateTime;
+import java.util.Map;
+import java.util.UUID;
+
+@Entity
+@Table(name = "audit_log")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class AuditLog {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID id;
+
+    @Column(name = "happened_at", nullable = false, updatable = false)
+    @CreationTimestamp
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private OffsetDateTime happenedAt;
+
+    @Column(name = "actor_id")
+    private UUID actorId;
+
+    @Enumerated(EnumType.STRING)
+    @Column(name = "kind", nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private AuditKind kind;
+
+    @Column(name = "document_id")
+    private UUID documentId;
+
+    @JdbcTypeCode(SqlTypes.JSON)
+    @Column(columnDefinition = "jsonb")
+    private Map<String, Object> payload;
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditLogQueryRepository.java

@@ -0,0 +1,200 @@
+package org.raddatz.familienarchiv.audit;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.time.OffsetDateTime;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import java.util.UUID;
+
+public interface AuditLogQueryRepository extends JpaRepository<AuditLog, UUID> {
+
+    @Query(value = """
+            SELECT a.document_id
+            FROM audit_log a
+            WHERE a.kind IN ('TEXT_SAVED', 'ANNOTATION_CREATED')
+              AND a.actor_id = :userId
+              AND a.document_id IS NOT NULL
+            ORDER BY a.happened_at DESC
+            LIMIT 1
+            """, nativeQuery = true)
+    Optional<UUID> findMostRecentDocumentIdByActor(@Param("userId") UUID userId);
+
+    @Query(value = """
+            WITH events AS (
+                SELECT
+                    a.kind,
+                    a.actor_id,
+                    a.document_id,
+                    a.happened_at,
+                    a.payload,
+                    LAG(a.happened_at) OVER (
+                        PARTITION BY a.actor_id, a.document_id, a.kind
+                        ORDER BY a.happened_at
+                    ) AS prev_happened_at
+                FROM audit_log a
+                WHERE a.kind IN (:kinds)
+                  AND a.document_id IS NOT NULL
+            ),
+            sessions_marked AS (
+                SELECT
+                    kind, actor_id, document_id, happened_at, payload,
+                    CASE
+                        WHEN kind IN ('COMMENT_ADDED','MENTION_CREATED') THEN 1
+                        WHEN prev_happened_at IS NULL THEN 1
+                        WHEN EXTRACT(EPOCH FROM (happened_at - prev_happened_at)) > 7200 THEN 1
+                        ELSE 0
+                    END AS is_new_session
+                FROM events
+            ),
+            sessions AS (
+                SELECT
+                    kind, actor_id, document_id, happened_at, payload,
+                    SUM(is_new_session) OVER (
+                        PARTITION BY actor_id, document_id, kind
+                        ORDER BY happened_at
+                        ROWS UNBOUNDED PRECEDING
+                    ) AS session_id
+                FROM sessions_marked
+            ),
+            aggregated AS (
+                SELECT
+                    s.kind,
+                    s.actor_id,
+                    s.document_id,
+                    s.session_id,
+                    MIN(s.happened_at)                                            AS happened_at,
+                    CASE WHEN COUNT(*) > 1 THEN MAX(s.happened_at) ELSE NULL END  AS happened_at_until,
+                    COUNT(*)::int                                                 AS count,
+                    BOOL_OR(s.kind = 'MENTION_CREATED'
+                        AND s.payload->>'mentionedUserId' = :currentUserId)       AS you_mentioned,
+                    -- COMMENT_ADDED/MENTION_CREATED always have is_new_session=1, so each group has one row and MIN collapses to that row payload
+                    MIN(s.payload::text)::jsonb                                   AS payload
+                FROM sessions s
+                GROUP BY s.kind, s.actor_id, s.document_id, s.session_id
+            )
+            SELECT
+                ag.kind                                                AS kind,
+                ag.actor_id                                            AS actorId,
+                CASE
+                    WHEN u.first_name IS NOT NULL AND u.last_name IS NOT NULL
+                        THEN UPPER(LEFT(u.first_name, 1)) || UPPER(LEFT(u.last_name, 1))
+                    WHEN u.first_name IS NOT NULL THEN UPPER(LEFT(u.first_name, 1))
+                    WHEN u.last_name  IS NOT NULL THEN UPPER(LEFT(u.last_name, 1))
+                    ELSE '?'
+                END                                                    AS actorInitials,
+                COALESCE(u.color, '')                                  AS actorColor,
+                CONCAT_WS(' ', u.first_name, u.last_name)             AS actorName,
+                ag.document_id                                         AS documentId,
+                ag.happened_at                                         AS happened_at,
+                ag.you_mentioned                                       AS youMentioned,
+                -- payload->>'commentId' matches notifications.reference_id per AuditKind.COMMENT_ADDED contract
+                EXISTS(
+                    SELECT 1 FROM notifications n
+                    WHERE n.type = 'REPLY'
+                      AND n.recipient_id = CAST(:currentUserId AS uuid)
+                      AND n.reference_id = (ag.payload->>'commentId')::uuid
+                )                                                      AS youParticipated,
+                ag.count                                               AS count,
+                ag.happened_at_until                                   AS happenedAtUntil,
+                (ag.payload->>'commentId')::uuid                       AS commentId
+            FROM aggregated ag
+            LEFT JOIN users u ON u.id = ag.actor_id
+            ORDER BY ag.happened_at DESC
+            LIMIT :limit
+            """, nativeQuery = true)
+    List<ActivityFeedRow> findRolledUpActivityFeed(
+            @Param("currentUserId") String currentUserId,
+            @Param("limit") int limit,
+            @Param("kinds") Collection<String> kinds);
+
+    @Query(value = """
+            SELECT
+                COUNT(DISTINCT (a.document_id::text || '|' || (a.payload->>'pageNumber'))) AS pages,
+                COUNT(*) FILTER (WHERE a.kind = 'ANNOTATION_CREATED')                     AS annotated,
+                COUNT(DISTINCT a.payload->>'blockId') FILTER (WHERE a.kind = 'TEXT_SAVED') AS transcribed,
+                COUNT(DISTINCT a.document_id) FILTER (WHERE a.kind = 'FILE_UPLOADED')      AS uploaded,
+                COUNT(DISTINCT (a.document_id::text || '|' || (a.payload->>'pageNumber')))
+                    FILTER (WHERE (a.kind = 'ANNOTATION_CREATED' OR a.kind = 'TEXT_SAVED')
+                            AND a.actor_id::text = :userId)                                AS yourPages
+            FROM audit_log a
+            WHERE a.happened_at >= :weekStart
+              AND a.kind IN ('ANNOTATION_CREATED','TEXT_SAVED','FILE_UPLOADED')
+            """, nativeQuery = true)
+    PulseStatsRow getPulseStats(
+            @Param("weekStart") OffsetDateTime weekStart,
+            @Param("userId") String userId);
+
+    @Query(value = """
+            SELECT DISTINCT ON (a.document_id)
+                a.document_id AS documentId,
+                a.actor_id    AS actorId
+            FROM audit_log a
+            WHERE a.kind = :kind
+              AND a.document_id IN :documentIds
+              AND a.actor_id IS NOT NULL
+            ORDER BY a.document_id, a.happened_at DESC
+            """, nativeQuery = true)
+    List<Object[]> findMostRecentActorPerDocument(
+            @Param("documentIds") List<UUID> documentIds,
+            @Param("kind") String kind);
+
+    @Query(value = """
+            SELECT
+                a.document_id                                                    AS documentId,
+                CASE
+                    WHEN u.first_name IS NOT NULL AND u.last_name IS NOT NULL
+                        THEN UPPER(LEFT(u.first_name, 1)) || UPPER(LEFT(u.last_name, 1))
+                    WHEN u.first_name IS NOT NULL THEN UPPER(LEFT(u.first_name, 1))
+                    WHEN u.last_name  IS NOT NULL THEN UPPER(LEFT(u.last_name, 1))
+                    ELSE '?'
+                END                                                              AS actorInitials,
+                COALESCE(u.color, '')                                            AS actorColor,
+                CONCAT_WS(' ', u.first_name, u.last_name)                       AS actorName
+            FROM audit_log a
+            LEFT JOIN users u ON u.id = a.actor_id
+            WHERE a.kind IN ('ANNOTATION_CREATED', 'TEXT_SAVED', 'BLOCK_REVIEWED')
+              AND a.document_id IN :documentIds
+              AND a.actor_id IS NOT NULL
+            GROUP BY a.document_id, a.actor_id, u.first_name, u.last_name, u.color
+            ORDER BY a.document_id, MIN(a.happened_at)
+            """, nativeQuery = true)
+    List<ContributorRow> findContributorsPerDocument(@Param("documentIds") List<UUID> documentIds);
+
+    @Query(value = """
+            SELECT
+                ranked.document_id   AS documentId,
+                ranked.actorInitials AS actorInitials,
+                ranked.actorColor    AS actorColor,
+                ranked.actorName     AS actorName
+            FROM (
+                SELECT
+                    a.document_id,
+                    CASE
+                        WHEN u.first_name IS NOT NULL AND u.last_name IS NOT NULL
+                            THEN UPPER(LEFT(u.first_name, 1)) || UPPER(LEFT(u.last_name, 1))
+                        WHEN u.first_name IS NOT NULL THEN UPPER(LEFT(u.first_name, 1))
+                        WHEN u.last_name  IS NOT NULL THEN UPPER(LEFT(u.last_name, 1))
+                        ELSE '?'
+                    END                                                        AS actorInitials,
+                    COALESCE(u.color, '')                                      AS actorColor,
+                    NULLIF(CONCAT_WS(' ', u.first_name, u.last_name), '')     AS actorName,
+                    ROW_NUMBER() OVER (
+                        PARTITION BY a.document_id
+                        ORDER BY MAX(a.happened_at) DESC
+                    )                                                          AS rn
+                FROM audit_log a
+                LEFT JOIN users u ON u.id = a.actor_id
+                WHERE a.kind IN ('ANNOTATION_CREATED', 'TEXT_SAVED', 'BLOCK_REVIEWED')
+                  AND a.document_id IN :documentIds
+                  AND a.actor_id IS NOT NULL
+                GROUP BY a.document_id, a.actor_id, u.first_name, u.last_name, u.color
+            ) ranked
+            WHERE ranked.rn <= 4
+            ORDER BY ranked.document_id, ranked.rn
+            """, nativeQuery = true)
+    List<ContributorRow> findRecentContributorsForDocuments(@Param("documentIds") List<UUID> documentIds);
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditLogQueryService.java

@@ -0,0 +1,62 @@
+package org.raddatz.familienarchiv.audit;
+
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+import java.time.OffsetDateTime;
+import java.util.*;
+
+@Service
+@RequiredArgsConstructor
+public class AuditLogQueryService {
+
+    private final AuditLogQueryRepository queryRepository;
+
+    public Optional<UUID> findMostRecentDocumentForUser(UUID userId) {
+        return queryRepository.findMostRecentDocumentIdByActor(userId);
+    }
+
+    public List<ActivityFeedRow> findActivityFeed(UUID currentUserId, int limit) {
+        return findActivityFeed(currentUserId, limit, AuditKind.ROLLUP_ELIGIBLE);
+    }
+
+    public List<ActivityFeedRow> findActivityFeed(UUID currentUserId, int limit, Set<AuditKind> kinds) {
+        List<String> kindNames = kinds.stream().map(Enum::name).toList();
+        return queryRepository.findRolledUpActivityFeed(currentUserId.toString(), limit, kindNames);
+    }
+
+    public PulseStatsRow getPulseStats(OffsetDateTime weekStart, UUID userId) {
+        return queryRepository.getPulseStats(weekStart, userId.toString());
+    }
+
+    public Map<UUID, UUID> findMostRecentActorPerDocument(List<UUID> documentIds, String kind) {
+        if (documentIds.isEmpty()) return Map.of();
+        List<Object[]> rows = queryRepository.findMostRecentActorPerDocument(documentIds, kind);
+        Map<UUID, UUID> result = new LinkedHashMap<>();
+        for (Object[] row : rows) {
+            UUID docId = (UUID) row[0];
+            UUID actorId = (UUID) row[1];
+            result.put(docId, actorId);
+        }
+        return result;
+    }
+
+    public Map<UUID, List<ActivityActorDTO>> findContributorsPerDocument(List<UUID> documentIds) {
+        if (documentIds.isEmpty()) return Map.of();
+        return toContributorMap(queryRepository.findContributorsPerDocument(documentIds));
+    }
+
+    public Map<UUID, List<ActivityActorDTO>> findRecentContributorsPerDocument(List<UUID> documentIds) {
+        if (documentIds.isEmpty()) return Map.of();
+        return toContributorMap(queryRepository.findRecentContributorsForDocuments(documentIds));
+    }
+
+    private Map<UUID, List<ActivityActorDTO>> toContributorMap(List<ContributorRow> rows) {
+        Map<UUID, List<ActivityActorDTO>> result = new LinkedHashMap<>();
+        for (ContributorRow row : rows) {
+            result.computeIfAbsent(row.getDocumentId(), k -> new ArrayList<>())
+                  .add(new ActivityActorDTO(row.getActorInitials(), row.getActorColor(), row.getActorName()));
+        }
+        return result;
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditLogRepository.java

@@ -0,0 +1,8 @@
+package org.raddatz.familienarchiv.audit;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.UUID;
+
+public interface AuditLogRepository extends JpaRepository<AuditLog, UUID> {
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/AuditService.java

@@ -0,0 +1,57 @@
+package org.raddatz.familienarchiv.audit;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.core.task.TaskExecutor;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.support.TransactionSynchronization;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import java.util.Map;
+import java.util.UUID;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class AuditService {
+
+    private final AuditLogRepository auditLogRepository;
+    @Qualifier("auditExecutor")
+    private final TaskExecutor auditExecutor;
+
+    @Async("auditExecutor")
+    public void log(AuditKind kind, UUID actorId, UUID documentId, Map<String, Object> payload) {
+        writeLog(kind, actorId, documentId, payload);
+    }
+
+    public void logAfterCommit(AuditKind kind, UUID actorId, UUID documentId, Map<String, Object> payload) {
+        if (TransactionSynchronizationManager.isActualTransactionActive()) {
+            TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
+                @Override
+                public void afterCommit() {
+                    // Run on a separate thread: the afterCommit() callback fires while Spring's
+                    // transaction synchronizations are still active on the current thread, which
+                    // prevents SimpleJpaRepository.save() from starting a new transaction inline.
+                    auditExecutor.execute(() -> writeLog(kind, actorId, documentId, payload));
+                }
+            });
+        } else {
+            writeLog(kind, actorId, documentId, payload);
+        }
+    }
+
+    private void writeLog(AuditKind kind, UUID actorId, UUID documentId, Map<String, Object> payload) {
+        try {
+            auditLogRepository.save(AuditLog.builder()
+                    .kind(kind)
+                    .actorId(actorId)
+                    .documentId(documentId)
+                    .payload(payload)
+                    .build());
+        } catch (Exception e) {
+            log.error("Audit log write failed: kind={}, document={}", kind, documentId, e);
+        }
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/ContributorRow.java

@@ -0,0 +1,10 @@
+package org.raddatz.familienarchiv.audit;
+
+import java.util.UUID;
+
+public interface ContributorRow {
+    UUID getDocumentId();
+    String getActorInitials();
+    String getActorColor();
+    String getActorName();
+}

backend/src/main/java/org/raddatz/familienarchiv/audit/PulseStatsRow.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.audit;
+
+public interface PulseStatsRow {
+    long getPages();
+    long getAnnotated();
+    long getTranscribed();
+    long getUploaded();
+    long getYourPages();
+}

backend/src/main/java/org/raddatz/familienarchiv/config/AsyncConfig.java

@@ -23,4 +23,33 @@ public class AsyncConfig {
         executor.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
         return executor;
     }
+
+    @Bean("auditExecutor")
+    public Executor auditExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(1);
+        executor.setMaxPoolSize(2);
+        executor.setQueueCapacity(50);
+        executor.setThreadNamePrefix("Audit-");
+        // AbortPolicy instead of CallerRunsPolicy: if CallerRunsPolicy ran the task on the
+        // afterCommit() callback thread, Spring's transaction synchronizations would still be
+        // active on that thread and SimpleJpaRepository.save() would throw IllegalStateException.
+        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
+        return executor;
+    }
+
+    @Bean("thumbnailExecutor")
+    public Executor thumbnailExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(1);
+        executor.setMaxPoolSize(2);
+        executor.setQueueCapacity(200);
+        executor.setThreadNamePrefix("Thumbnail-");
+        // CallerRunsPolicy applies back-pressure to quick-upload batches and admin backfill
+        // instead of dropping work (shared taskExecutor uses AbortPolicy). Safe because the
+        // task is dispatched via TransactionSynchronization.afterCommit, which runs on a
+        // post-commit callback thread without active transaction synchronization.
+        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
+        return executor;
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/config/DataInitializer.java

@@ -31,8 +31,8 @@ import java.util.Set;
 @DependsOn("flyway")
 public class DataInitializer {
 
-    @Value("${app.admin.username:admin}")
-    private String adminUsername;
+    @Value("${app.admin.email:admin@familyarchive.local}")
+    private String adminEmail;
 
     @Value("${app.admin.password:admin123}")
     private String adminPassword;
@@ -43,26 +43,23 @@ public class DataInitializer {
     @Bean
     public CommandLineRunner initAdminUser(PasswordEncoder passwordEncoder) {
         return args -> {
-            if (userRepository.findByUsername(adminUsername).isEmpty()) {
-                log.info("Kein Admin-User '{}' gefunden. Erstelle Default-Admin...", adminUsername);
+            if (userRepository.findByEmail(adminEmail).isEmpty()) {
+                log.info("Kein Admin-User '{}' gefunden. Erstelle Default-Admin...", adminEmail);
 
-                // 1. Admin Gruppe erstellen
                 UserGroup adminGroup = UserGroup.builder()
                         .name("Administrators")
                         .permissions(Set.of("ADMIN", "READ_ALL", "WRITE_ALL", "ANNOTATE_ALL", "ADMIN_USER", "ADMIN_TAG", "ADMIN_PERMISSION"))
                         .build();
                 groupRepository.save(adminGroup);
 
-                // 2. Admin User erstellen
                 AppUser admin = AppUser.builder()
-                        .username(adminUsername)
-                        .password(passwordEncoder.encode(adminPassword)) // Passwort verschlüsseln!
-                        .email("admin@familyarchive.local")
+                        .email(adminEmail)
+                        .password(passwordEncoder.encode(adminPassword))
                         .groups(Set.of(adminGroup))
                         .build();
                 userRepository.save(admin);
 
-                log.info("Default Admin erstellt: User='{}'", adminUsername);
+                log.info("Default Admin erstellt: Email='{}'", adminEmail);
             }
         };
     }
@@ -84,16 +81,13 @@ public class DataInitializer {
             TagRepository tagRepo,
             PasswordEncoder passwordEncoder) {
         return args -> {
-            // Always reset the admin password to the configured value so a failed password-reset
-            // test from a previous run can never leave the account locked out.
-            userRepository.findByUsername(adminUsername).ifPresent(admin -> {
+            userRepository.findByEmail(adminEmail).ifPresent(admin -> {
                 admin.setPassword(passwordEncoder.encode(adminPassword));
                 userRepository.save(admin);
                 log.info("E2E seed: Admin-Passwort auf konfigurierten Wert zurückgesetzt.");
             });
 
-            // Always ensure the read-only test user exists, even when seed data was already loaded.
-            if (userRepository.findByUsername("reader").isEmpty()) {
+            if (userRepository.findByEmail("reader@familyarchive.local").isEmpty()) {
                 log.info("E2E seed: Erstelle 'reader'-Testbenutzer...");
                 UserGroup leserGroup = groupRepository.findByName("Leser").orElseGet(() ->
                         groupRepository.save(UserGroup.builder()
@@ -101,7 +95,7 @@ public class DataInitializer {
                                 .permissions(Set.of("READ_ALL"))
                                 .build()));
                 userRepository.save(AppUser.builder()
-                        .username("reader")
+                        .email("reader@familyarchive.local")
                         .password(passwordEncoder.encode("reader123"))
                         .groups(Set.of(leserGroup))
                         .build());
@@ -131,7 +125,6 @@ public class DataInitializer {
             Tag tagUrlaub  = tagRepo.save(Tag.builder().name("Urlaub").build());
 
             // ── Documents ────────────────────────────────────────────────────
-            // 1. Fully transcribed letter — used by search + detail E2E tests
             docRepo.save(Document.builder()
                     .title("Geburtsurkunde Hans Müller")
                     .originalFilename("geburtsurkunde_hans.pdf")
@@ -144,7 +137,6 @@ public class DataInitializer {
                     .transcription("Hiermit wird beurkundet, dass Hans Müller am 12. April 1923 in Berlin geboren wurde.")
                     .build());
 
-            // 2. Letter with multiple receivers and tags — tests multi-receiver display
             docRepo.save(Document.builder()
                     .title("Brief aus dem Krieg")
                     .originalFilename("brief_krieg_1944.pdf")
@@ -157,7 +149,6 @@ public class DataInitializer {
                     .transcription("Liebe Anna, ich schreibe dir aus der Front. Es geht mir den Umständen entsprechend gut.")
                     .build());
 
-            // 3. Postcard — no transcription, tests PLACEHOLDER status
             docRepo.save(Document.builder()
                     .title("Urlaubspostkarte Ostsee")
                     .originalFilename("postkarte_1965.jpg")
@@ -169,7 +160,6 @@ public class DataInitializer {
                     .tags(Set.of(tagUrlaub))
                     .build());
 
-            // 4. Document with no sender — tests null-sender display ("Unbekannt")
             docRepo.save(Document.builder()
                     .title("Unbekanntes Dokument")
                     .originalFilename("unbekannt.pdf")
@@ -179,7 +169,6 @@ public class DataInitializer {
                     .receivers(Set.of(maria))
                     .build());
 
-            // 5. Document with minimal metadata — tests sparse display
             docRepo.save(Document.builder()
                     .title("Scan ohne Titel")
                     .originalFilename("scan_ohne_titel.pdf")

backend/src/main/java/org/raddatz/familienarchiv/config/RateLimitInterceptor.java

@@ -0,0 +1,69 @@
+package org.raddatz.familienarchiv.config;
+
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.servlet.HandlerInterceptor;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class RateLimitInterceptor implements HandlerInterceptor {
+
+    private static final int MAX_REQUESTS_PER_MINUTE = 10;
+
+    // Caffeine cache: per-IP counter that expires 1 minute after first access.
+    // Bounded to 10_000 entries to prevent OOM from IP exhaustion.
+    private final Cache<String, AtomicInteger> requestCounts = Caffeine.newBuilder()
+            .expireAfterAccess(1, TimeUnit.MINUTES)
+            .maximumSize(10_000)
+            .build();
+
+    @Override
+    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
+            throws Exception {
+        String ip = resolveClientIp(request);
+        AtomicInteger count = requestCounts.get(ip, k -> new AtomicInteger(0));
+        if (count.incrementAndGet() > MAX_REQUESTS_PER_MINUTE) {
+            response.setStatus(HttpStatus.TOO_MANY_REQUESTS.value());
+            response.getWriter().write("{\"code\":\"RATE_LIMIT_EXCEEDED\",\"message\":\"Too many requests\"}");
+            return false;
+        }
+        return true;
+    }
+
+    private String resolveClientIp(HttpServletRequest request) {
+        // Only trust X-Forwarded-For when the direct connection comes from a known
+        // reverse proxy (loopback or Docker private network). Trusting it unconditionally
+        // allows any client to spoof a different IP and bypass per-IP rate limiting.
+        String remoteAddr = request.getRemoteAddr();
+        if (isTrustedProxy(remoteAddr)) {
+            String forwarded = request.getHeader("X-Forwarded-For");
+            if (forwarded != null && !forwarded.isBlank()) {
+                return forwarded.split(",")[0].trim();
+            }
+        }
+        return remoteAddr;
+    }
+
+    private boolean isTrustedProxy(String ip) {
+        if (ip.equals("127.0.0.1") || ip.equals("::1") || ip.startsWith("10.") || ip.startsWith("192.168.")) {
+            return true;
+        }
+        // Only RFC 1918 172.16.0.0/12 (172.16–172.31), not all of 172.x
+        if (ip.startsWith("172.")) {
+            String[] parts = ip.split("\\.");
+            if (parts.length >= 2) {
+                try {
+                    int second = Integer.parseInt(parts[1]);
+                    return second >= 16 && second <= 31;
+                } catch (NumberFormatException ignored) {
+                    return false;
+                }
+            }
+        }
+        return false;
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/config/SecurityConfig.java

@@ -50,6 +50,8 @@ public class SecurityConfig {
                     auth.requestMatchers("/actuator/health").permitAll();
                     // Password reset endpoints are unauthenticated by nature
                     auth.requestMatchers("/api/auth/forgot-password", "/api/auth/reset-password").permitAll();
+                    // Invite-based registration endpoints are public
+                    auth.requestMatchers("/api/auth/invite/**", "/api/auth/register").permitAll();
                     // E2E test helper (only active under "e2e" profile)
                     auth.requestMatchers("/api/auth/reset-token-for-test").permitAll();
                     // In dev, allow unauthenticated access to the OpenAPI spec and Swagger UI
@@ -67,7 +69,7 @@ public class SecurityConfig {
                         .frameOptions(frameOptions -> frameOptions.sameOrigin()))
                 // Erlaubt Login via Browser-Popup oder REST-Header (Authorization: Basic ...)
                 .httpBasic(Customizer.withDefaults())
-                .formLogin(Customizer.withDefaults());
+                .formLogin(form -> form.usernameParameter("email"));
 
         return http.build();
     }

backend/src/main/java/org/raddatz/familienarchiv/config/WebConfig.java

@@ -0,0 +1,15 @@
+package org.raddatz.familienarchiv.config;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Configuration
+public class WebConfig implements WebMvcConfigurer {
+
+    @Override
+    public void addInterceptors(InterceptorRegistry registry) {
+        registry.addInterceptor(new RateLimitInterceptor())
+                .addPathPatterns("/api/auth/invite/**", "/api/auth/register");
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/controller/AdminController.java

@@ -6,6 +6,7 @@ import org.raddatz.familienarchiv.security.RequirePermission;
 import org.raddatz.familienarchiv.service.DocumentService;
 import org.raddatz.familienarchiv.service.DocumentVersionService;
 import org.raddatz.familienarchiv.service.MassImportService;
+import org.raddatz.familienarchiv.service.ThumbnailBackfillService;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -23,6 +24,7 @@ public class AdminController {
     private final MassImportService massImportService;
     private final DocumentService documentService;
     private final DocumentVersionService documentVersionService;
+    private final ThumbnailBackfillService thumbnailBackfillService;
 
     @PostMapping("/trigger-import")
     public ResponseEntity<MassImportService.ImportStatus> triggerMassImport() {
@@ -47,4 +49,15 @@ public class AdminController {
         int count = documentService.backfillFileHashes();
         return ResponseEntity.ok(new BackfillResult(count));
     }
+
+    @PostMapping("/generate-thumbnails")
+    public ResponseEntity<ThumbnailBackfillService.BackfillStatus> generateThumbnails() {
+        thumbnailBackfillService.runBackfillAsync();
+        return ResponseEntity.accepted().body(thumbnailBackfillService.getStatus());
+    }
+
+    @GetMapping("/thumbnail-status")
+    public ResponseEntity<ThumbnailBackfillService.BackfillStatus> thumbnailStatus() {
+        return ResponseEntity.ok(thumbnailBackfillService.getStatus());
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/AnnotationController.java

@@ -72,7 +72,7 @@ public class AnnotationController {
     private UUID resolveUserId(Authentication authentication) {
         if (authentication == null || !authentication.isAuthenticated()) return null;
         try {
-            AppUser user = userService.findByUsername(authentication.getName());
+            AppUser user = userService.findByEmail(authentication.getName());
             return user != null ? user.getId() : null;
         } catch (Exception e) {
             log.warn("Could not resolve user for annotation: {}", e.getMessage());

backend/src/main/java/org/raddatz/familienarchiv/controller/AuthController.java

@@ -1,14 +1,18 @@
 package org.raddatz.familienarchiv.controller;
 
+import jakarta.validation.Valid;
 import org.raddatz.familienarchiv.dto.ForgotPasswordRequest;
+import org.raddatz.familienarchiv.dto.InvitePrefillDTO;
+import org.raddatz.familienarchiv.dto.RegisterRequest;
 import org.raddatz.familienarchiv.dto.ResetPasswordRequest;
+import org.raddatz.familienarchiv.model.AppUser;
+import org.raddatz.familienarchiv.model.InviteToken;
+import org.raddatz.familienarchiv.service.InviteService;
 import org.raddatz.familienarchiv.service.PasswordResetService;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
-import org.springframework.web.bind.annotation.PostMapping;
-import org.springframework.web.bind.annotation.RequestBody;
-import org.springframework.web.bind.annotation.RequestMapping;
-import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.bind.annotation.*;
 
 import lombok.RequiredArgsConstructor;
 
@@ -18,6 +22,7 @@ import lombok.RequiredArgsConstructor;
 public class AuthController {
 
     private final PasswordResetService passwordResetService;
+    private final InviteService inviteService;
 
     @Value("${app.base-url:http://localhost:3000}")
     private String appBaseUrl;
@@ -34,4 +39,20 @@ public class AuthController {
         passwordResetService.resetPassword(request);
         return ResponseEntity.noContent().build();
     }
+
+    @GetMapping("/invite/{code}")
+    public InvitePrefillDTO getInvitePrefill(@PathVariable String code) {
+        InviteToken token = inviteService.validateCode(code);
+        return new InvitePrefillDTO(
+                token.getPrefillFirstName(),
+                token.getPrefillLastName(),
+                token.getPrefillEmail()
+        );
+    }
+
+    @PostMapping("/register")
+    public ResponseEntity<AppUser> register(@Valid @RequestBody RegisterRequest request) {
+        AppUser user = inviteService.redeemInvite(request);
+        return ResponseEntity.status(HttpStatus.CREATED).body(user);
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/CommentController.java

@@ -24,67 +24,6 @@ public class CommentController {
     private final CommentService commentService;
     private final UserService userService;
 
-    // ─── General document comments ────────────────────────────────────────────
-
-    @GetMapping("/api/documents/{documentId}/comments")
-    public List<DocumentComment> getDocumentComments(@PathVariable UUID documentId) {
-        return commentService.getCommentsForDocument(documentId);
-    }
-
-    @PostMapping("/api/documents/{documentId}/comments")
-    @ResponseStatus(HttpStatus.CREATED)
-    @RequirePermission({Permission.ANNOTATE_ALL, Permission.WRITE_ALL})
-    public DocumentComment postDocumentComment(
-            @PathVariable UUID documentId,
-            @RequestBody CreateCommentDTO dto,
-            Authentication authentication) {
-        AppUser author = resolveUser(authentication);
-        return commentService.postComment(documentId, null, dto.getContent(), dto.getMentionedUserIds(), author);
-    }
-
-    @PostMapping("/api/documents/{documentId}/comments/{commentId}/replies")
-    @ResponseStatus(HttpStatus.CREATED)
-    @RequirePermission({Permission.ANNOTATE_ALL, Permission.WRITE_ALL})
-    public DocumentComment replyToDocumentComment(
-            @PathVariable UUID documentId,
-            @PathVariable UUID commentId,
-            @RequestBody CreateCommentDTO dto,
-            Authentication authentication) {
-        AppUser author = resolveUser(authentication);
-        return commentService.replyToComment(documentId, commentId, dto.getContent(), dto.getMentionedUserIds(), author);
-    }
-
-    // ─── Annotation comments ──────────────────────────────────────────────────
-
-    @GetMapping("/api/documents/{documentId}/annotations/{annotationId}/comments")
-    public List<DocumentComment> getAnnotationComments(@PathVariable UUID annotationId) {
-        return commentService.getCommentsForAnnotation(annotationId);
-    }
-
-    @PostMapping("/api/documents/{documentId}/annotations/{annotationId}/comments")
-    @ResponseStatus(HttpStatus.CREATED)
-    @RequirePermission({Permission.ANNOTATE_ALL, Permission.WRITE_ALL})
-    public DocumentComment postAnnotationComment(
-            @PathVariable UUID documentId,
-            @PathVariable UUID annotationId,
-            @RequestBody CreateCommentDTO dto,
-            Authentication authentication) {
-        AppUser author = resolveUser(authentication);
-        return commentService.postComment(documentId, annotationId, dto.getContent(), dto.getMentionedUserIds(), author);
-    }
-
-    @PostMapping("/api/documents/{documentId}/annotations/{annotationId}/comments/{commentId}/replies")
-    @ResponseStatus(HttpStatus.CREATED)
-    @RequirePermission({Permission.ANNOTATE_ALL, Permission.WRITE_ALL})
-    public DocumentComment replyToAnnotationComment(
-            @PathVariable UUID documentId,
-            @PathVariable UUID commentId,
-            @RequestBody CreateCommentDTO dto,
-            Authentication authentication) {
-        AppUser author = resolveUser(authentication);
-        return commentService.replyToComment(documentId, commentId, dto.getContent(), dto.getMentionedUserIds(), author);
-    }
-
     // ─── Block (transcription) comments ────────────────────────────────────────
 
     @GetMapping("/api/documents/{documentId}/transcription-blocks/{blockId}/comments")
@@ -144,7 +83,7 @@ public class CommentController {
     private AppUser resolveUser(Authentication authentication) {
         if (authentication == null || !authentication.isAuthenticated()) return null;
         try {
-            return userService.findByUsername(authentication.getName());
+            return userService.findByEmail(authentication.getName());
         } catch (Exception e) {
             log.warn("Could not resolve user for comment: {}", e.getMessage());
             return null;

backend/src/main/java/org/raddatz/familienarchiv/controller/DocumentController.java

@@ -3,6 +3,7 @@ package org.raddatz.familienarchiv.controller;
 import java.io.IOException;
 import java.time.LocalDate;
 import java.util.ArrayList;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -13,8 +14,21 @@ import java.util.UUID;
 
 import io.swagger.v3.oas.annotations.Parameter;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import jakarta.validation.Valid;
+import jakarta.validation.constraints.Max;
+import jakarta.validation.constraints.Min;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.validation.annotation.Validated;
+import org.raddatz.familienarchiv.dto.BatchMetadataRequest;
+import org.raddatz.familienarchiv.dto.BulkEditError;
+import org.raddatz.familienarchiv.dto.BulkEditResult;
+import org.raddatz.familienarchiv.dto.DocumentBatchMetadataDTO;
+import org.raddatz.familienarchiv.dto.DocumentBatchSummary;
+import org.raddatz.familienarchiv.dto.DocumentBulkEditDTO;
 import org.raddatz.familienarchiv.dto.DocumentSearchResult;
 import org.raddatz.familienarchiv.dto.DocumentUpdateDTO;
+import org.raddatz.familienarchiv.dto.TagOperator;
 import org.raddatz.familienarchiv.dto.DocumentVersionSummary;
 import org.raddatz.familienarchiv.dto.IncompleteDocumentDTO;
 import org.raddatz.familienarchiv.exception.DomainException;
@@ -24,12 +38,16 @@ import org.raddatz.familienarchiv.dto.DocumentSort;
 import org.raddatz.familienarchiv.model.DocumentStatus;
 import org.raddatz.familienarchiv.model.TrainingLabel;
 import org.raddatz.familienarchiv.model.DocumentVersion;
+import org.raddatz.familienarchiv.model.AppUser;
 import org.raddatz.familienarchiv.security.Permission;
 import org.raddatz.familienarchiv.security.RequirePermission;
+import org.raddatz.familienarchiv.security.SecurityUtils;
 import org.raddatz.familienarchiv.service.DocumentService;
 import org.raddatz.familienarchiv.service.DocumentVersionService;
 import org.raddatz.familienarchiv.service.FileService;
+import org.raddatz.familienarchiv.service.UserService;
 import org.springframework.data.domain.Sort;
+import org.springframework.security.core.Authentication;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
@@ -57,11 +75,13 @@ import lombok.extern.slf4j.Slf4j;
 @RequestMapping("/api/documents")
 @RequiredArgsConstructor
 @Slf4j
+@Validated
 public class DocumentController {
 
     private final DocumentService documentService;
     private final DocumentVersionService documentVersionService;
     private final FileService fileService;
+    private final UserService userService;
 
     // --- DOWNLOAD ---
     @GetMapping("/{id}/file")
@@ -88,6 +108,31 @@ public class DocumentController {
         }
     }
 
+    // --- THUMBNAIL ---
+    @GetMapping("/{id}/thumbnail")
+    public ResponseEntity<InputStreamResource> getDocumentThumbnail(@PathVariable UUID id) {
+        Document doc = documentService.getDocumentById(id);
+
+        if (doc.getThumbnailKey() == null) {
+            throw DomainException.notFound(ErrorCode.FILE_NOT_FOUND, "No thumbnail for document: " + id);
+        }
+
+        try {
+            FileService.S3FileDownload download = fileService.downloadFile(doc.getThumbnailKey());
+            return ResponseEntity.ok()
+                    .contentType(MediaType.IMAGE_JPEG)
+                    // `private` (not `public`) prevents shared caches from serving one user's
+                    // thumbnail to another (CWE-525). `immutable` is safe because the URL
+                    // carries a ?v=<thumbnailGeneratedAt> cache-buster that changes whenever
+                    // the underlying file is replaced.
+                    .header(HttpHeaders.CACHE_CONTROL, "private, max-age=31536000, immutable")
+                    .body(download.resource());
+        } catch (FileService.StorageFileNotFoundException e) {
+            throw DomainException.notFound(ErrorCode.FILE_NOT_FOUND,
+                    "Thumbnail missing in storage: " + doc.getThumbnailKey());
+        }
+    }
+
     // --- METADATA ---
     @GetMapping("/{id}")
     public Document getDocument(@PathVariable UUID id) {
@@ -111,9 +156,10 @@ public class DocumentController {
     public Document updateDocument(
             @PathVariable UUID id,
             @ModelAttribute DocumentUpdateDTO dto,
-            @RequestPart(value = "file", required = false) MultipartFile file) {
+            @RequestPart(value = "file", required = false) MultipartFile file,
+            Authentication authentication) {
         try {
-            return documentService.updateDocument(id, dto, file);
+            return documentService.updateDocument(id, dto, file, requireUserId(authentication));
         } catch (IOException e) {
             throw DomainException.internal(ErrorCode.FILE_UPLOAD_FAILED, "Failed to upload file: " + e.getMessage());
         }
@@ -128,18 +174,35 @@ public class DocumentController {
         return ResponseEntity.noContent().build();
     }
 
-    // --- QUICK UPLOAD ---
+    // --- ATTACH FILE ---
 
     private static final Set<String> ALLOWED_CONTENT_TYPES = Set.of(
             "application/pdf", "image/jpeg", "image/png", "image/tiff");
 
+    @PostMapping(value = "/{id}/file", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
+    @RequirePermission(Permission.WRITE_ALL)
+    public Document attachFile(
+            @PathVariable UUID id,
+            @RequestPart("file") MultipartFile file,
+            Authentication authentication) {
+        String contentType = file.getContentType();
+        if (contentType == null || !ALLOWED_CONTENT_TYPES.contains(contentType)) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "Unsupported file type: " + contentType);
+        }
+        return documentService.attachFile(id, file, requireUserId(authentication));
+    }
+
+    // --- QUICK UPLOAD ---
+
     public record UploadError(String filename, String code) {}
     public record QuickUploadResult(List<Document> created, List<Document> updated, List<UploadError> errors) {}
 
     @PostMapping(value = "/quick-upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
     @RequirePermission(Permission.WRITE_ALL)
     public QuickUploadResult quickUpload(
-            @RequestPart(value = "files", required = false) List<MultipartFile> files) {
+            @RequestPart(value = "files", required = false) List<MultipartFile> files,
+            @RequestPart(value = "metadata", required = false) DocumentBatchMetadataDTO metadata,
+            Authentication authentication) {
         List<Document> created = new ArrayList<>();
         List<Document> updated = new ArrayList<>();
         List<UploadError> errors = new ArrayList<>();
@@ -148,13 +211,21 @@ public class DocumentController {
             return new QuickUploadResult(created, updated, errors);
         }
 
-        for (MultipartFile file : files) {
+        documentService.validateBatch(files.size(), metadata);
+
+        UUID actorId = requireUserId(authentication);
+        long totalBytes = files.stream().mapToLong(MultipartFile::getSize).sum();
+
+        for (int i = 0; i < files.size(); i++) {
+            MultipartFile file = files.get(i);
             if (!ALLOWED_CONTENT_TYPES.contains(file.getContentType())) {
                 errors.add(new UploadError(file.getOriginalFilename(), "UNSUPPORTED_FILE_TYPE"));
                 continue;
             }
             try {
-                DocumentService.StoreResult result = documentService.storeDocument(file);
+                DocumentService.StoreResult result = metadata != null
+                        ? documentService.storeDocumentWithBatchMetadata(file, metadata, i, actorId)
+                        : documentService.storeDocument(file, actorId);
                 if (result.isNew()) {
                     created.add(result.document());
                 } else {
@@ -166,33 +237,129 @@ public class DocumentController {
             }
         }
 
+        log.info("quickUpload actor={} files={} totalBytes={} withMetadata={} created={} updated={} errors={}",
+                actorId, files.size(), totalBytes, metadata != null,
+                created.size(), updated.size(), errors.size());
+
         return new QuickUploadResult(created, updated, errors);
     }
 
+    // --- BULK EDIT ---
+
+    private static final int BULK_EDIT_MAX_IDS = 500;
+    /** Hard cap for {@code GET /api/documents/ids}: prevents an unfiltered
+     *  call from materialising the entire {@code documents} table into JSON.
+     *  Generous enough for real-world "Alle X editieren" against the family
+     *  archive's bounded scale (~1500 docs today, expected growth to ~5k). */
+    private static final int BULK_EDIT_FILTER_MAX_IDS = 5000;
+
+    @PatchMapping("/bulk")
+    @RequirePermission(Permission.WRITE_ALL)
+    public BulkEditResult patchBulk(
+            @RequestBody @Valid DocumentBulkEditDTO dto,
+            Authentication authentication) {
+        if (dto.getDocumentIds() == null || dto.getDocumentIds().isEmpty()) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "documentIds is required");
+        }
+        if (dto.getDocumentIds().size() > BULK_EDIT_MAX_IDS) {
+            throw DomainException.badRequest(ErrorCode.BULK_EDIT_TOO_MANY_IDS,
+                    "Maximum " + BULK_EDIT_MAX_IDS + " documents per request, got: " + dto.getDocumentIds().size());
+        }
+
+        UUID actorId = requireUserId(authentication);
+        int updated = 0;
+        List<BulkEditError> errors = new ArrayList<>();
+
+        // Dedupe duplicate document IDs while preserving submission order. A
+        // double-click on "Alle X editieren" would otherwise hit each document
+        // twice and inflate the `updated` count returned to the user.
+        LinkedHashSet<UUID> uniqueIds = new LinkedHashSet<>(dto.getDocumentIds());
+
+        for (UUID id : uniqueIds) {
+            try {
+                documentService.applyBulkEditToDocument(id, dto, actorId);
+                updated++;
+            } catch (DomainException e) {
+                errors.add(new BulkEditError(id, sanitizeForLog(e.getMessage())));
+            } catch (Exception e) {
+                errors.add(new BulkEditError(id, "Internal error"));
+                log.warn("Bulk edit failed for document {}: {}", id, sanitizeForLog(e.getMessage()));
+            }
+        }
+
+        log.info("bulkEdit actor={} documentIds={} unique={} updated={} errors={}",
+                actorId, dto.getDocumentIds().size(), uniqueIds.size(), updated, errors.size());
+
+        return new BulkEditResult(updated, errors);
+    }
+
+    /** CRLF strip for any log line interpolating a free-form string (e.g.
+     *  {@link Throwable#getMessage()}). Defends against CWE-117 log injection. */
+    private static String sanitizeForLog(String s) {
+        return s == null ? null : s.replaceAll("[\\r\\n]", "_");
+    }
+
+    @GetMapping("/ids")
+    @RequirePermission(Permission.WRITE_ALL)
+    public List<UUID> getDocumentIds(
+            @RequestParam(required = false) String q,
+            @RequestParam(required = false) LocalDate from,
+            @RequestParam(required = false) LocalDate to,
+            @RequestParam(required = false) UUID senderId,
+            @RequestParam(required = false) UUID receiverId,
+            @RequestParam(required = false, name = "tag") List<String> tags,
+            @RequestParam(required = false) String tagQ,
+            @RequestParam(required = false) DocumentStatus status,
+            @RequestParam(required = false) String tagOp,
+            Authentication authentication) {
+        TagOperator operator = "OR".equalsIgnoreCase(tagOp) ? TagOperator.OR : TagOperator.AND;
+        List<UUID> ids = documentService.findIdsForFilter(q, from, to, senderId, receiverId, tags, tagQ, status, operator);
+        if (ids.size() > BULK_EDIT_FILTER_MAX_IDS) {
+            throw DomainException.badRequest(ErrorCode.BULK_EDIT_TOO_MANY_IDS,
+                    "Filter matches " + ids.size() + " documents — refine filter (max " + BULK_EDIT_FILTER_MAX_IDS + ")");
+        }
+        UUID actorId = requireUserId(authentication);
+        log.info("documentIds actor={} matched={}", actorId, ids.size());
+        return ids;
+    }
+
+    @PostMapping(value = "/batch-metadata", consumes = MediaType.APPLICATION_JSON_VALUE)
+    @RequirePermission(Permission.READ_ALL)
+    public List<DocumentBatchSummary> batchMetadata(@RequestBody @Valid BatchMetadataRequest request, Authentication authentication) {
+        if (request == null || request.ids() == null || request.ids().isEmpty()) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "ids is required");
+        }
+        if (request.ids().size() > BULK_EDIT_MAX_IDS) {
+            throw DomainException.badRequest(ErrorCode.BULK_EDIT_TOO_MANY_IDS,
+                    "Maximum " + BULK_EDIT_MAX_IDS + " ids per request, got: " + request.ids().size());
+        }
+        UUID actorId = requireUserId(authentication);
+        log.info("batchMetadata actor={} ids={}", actorId, request.ids().size());
+        return documentService.batchMetadata(request.ids());
+    }
+
     @GetMapping("/incomplete-count")
+    @RequirePermission(Permission.WRITE_ALL)
     public Map<String, Long> getIncompleteCount() {
         return Map.of("count", documentService.getIncompleteCount());
     }
 
     @GetMapping("/incomplete")
+    @RequirePermission(Permission.WRITE_ALL)
     public List<IncompleteDocumentDTO> getIncomplete(
-            @Parameter(description = "Maximum number of results") @RequestParam(defaultValue = "10") int size) {
-        return documentService.findIncompleteDocuments(size);
+            @Parameter(description = "Maximum number of results (server caps at 200)")
+            @RequestParam(defaultValue = "50") int size) {
+        return documentService.findIncompleteDocuments(Math.min(size, 200));
     }
 
     @GetMapping("/incomplete/next")
+    @RequirePermission(Permission.WRITE_ALL)
     public ResponseEntity<Document> getNextIncomplete(@RequestParam UUID excludeId) {
         return documentService.findNextIncompleteDocument(excludeId)
                 .map(ResponseEntity::ok)
                 .orElse(ResponseEntity.noContent().build());
     }
 
-    @GetMapping("/recent-activity")
-    public ResponseEntity<List<Document>> getRecentActivity(
-            @RequestParam(defaultValue = "5") int size) {
-        return ResponseEntity.ok(documentService.getRecentActivity(size));
-    }
-
     @GetMapping("/search")
     public ResponseEntity<DocumentSearchResult> search(
             @RequestParam(required = false) String q,
@@ -204,12 +371,21 @@ public class DocumentController {
             @RequestParam(required = false) String tagQ,
             @Parameter(description = "Filter by document status") @RequestParam(required = false) DocumentStatus status,
             @Parameter(description = "Sort field") @RequestParam(required = false) DocumentSort sort,
-            @Parameter(description = "Sort direction: ASC or DESC") @RequestParam(required = false, defaultValue = "DESC") String dir) {
+            @Parameter(description = "Sort direction: ASC or DESC") @RequestParam(required = false, defaultValue = "DESC") String dir,
+            @Parameter(description = "Tag operator: AND (default) or OR") @RequestParam(required = false) String tagOp,
+            // @Max on page guards against overflow when pageable.getOffset() is computed
+            // as page * size — Integer.MAX_VALUE * 50 would wrap to a negative long, which
+            // Hibernate cheerfully turns into an invalid SQL OFFSET.
+            @Parameter(description = "Page number (0-indexed)") @RequestParam(defaultValue = "0") @Min(0) @Max(100_000) int page,
+            @Parameter(description = "Page size (max 100)") @RequestParam(defaultValue = "50") @Min(1) @Max(100) int size) {
         if (!"ASC".equalsIgnoreCase(dir) && !"DESC".equalsIgnoreCase(dir)) {
             throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "dir must be ASC or DESC");
         }
-        List<Document> results = documentService.searchDocuments(q, from, to, senderId, receiverId, tags, tagQ, status, sort, dir);
-        return ResponseEntity.ok(DocumentSearchResult.of(results));
+        // tagOp is a raw String at the HTTP boundary; any value other than "OR" (case-insensitive)
+        // defaults to AND, which matches the frontend default and keeps old clients working.
+        TagOperator operator = "OR".equalsIgnoreCase(tagOp) ? TagOperator.OR : TagOperator.AND;
+        Pageable pageable = PageRequest.of(page, size);
+        return ResponseEntity.ok(documentService.searchDocuments(q, from, to, senderId, receiverId, tags, tagQ, status, sort, dir, operator, pageable));
     }
 
     // --- TRAINING LABELS ---
@@ -258,4 +434,8 @@ public class DocumentController {
         Sort sort = Sort.by(Sort.Direction.fromString(dir.toUpperCase()), "documentDate");
         return documentService.getConversationFiltered(senderId, receiverId, from, to, sort);
     }
+
+    private UUID requireUserId(Authentication authentication) {
+        return SecurityUtils.requireUserId(authentication, userService);
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/InviteController.java

@@ -0,0 +1,57 @@
+package org.raddatz.familienarchiv.controller;
+
+import lombok.RequiredArgsConstructor;
+import org.raddatz.familienarchiv.dto.CreateInviteRequest;
+import org.raddatz.familienarchiv.dto.InviteListItemDTO;
+import org.raddatz.familienarchiv.model.AppUser;
+import org.raddatz.familienarchiv.security.Permission;
+import org.raddatz.familienarchiv.security.RequirePermission;
+import org.raddatz.familienarchiv.service.InviteService;
+import org.raddatz.familienarchiv.service.UserService;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.UUID;
+
+@RestController
+@RequestMapping("/api/invites")
+@RequiredArgsConstructor
+public class InviteController {
+
+    private final InviteService inviteService;
+    private final UserService userService;
+
+    @Value("${app.base-url:http://localhost:3000}")
+    private String appBaseUrl;
+
+    @GetMapping
+    @RequirePermission(Permission.ADMIN_USER)
+    public List<InviteListItemDTO> listInvites(
+            @RequestParam(value = "status", defaultValue = "active") String status) {
+        boolean activeOnly = !"all".equalsIgnoreCase(status);
+        return inviteService.listInvites(activeOnly, appBaseUrl);
+    }
+
+    @PostMapping
+    @RequirePermission(Permission.ADMIN_USER)
+    public ResponseEntity<InviteListItemDTO> createInvite(
+            @RequestBody CreateInviteRequest request,
+            @AuthenticationPrincipal UserDetails principal) {
+        AppUser creator = userService.findByEmail(principal.getUsername());
+        InviteListItemDTO created = inviteService.toListItemDTO(
+                inviteService.createInvite(request, creator), appBaseUrl);
+        return ResponseEntity.status(HttpStatus.CREATED).body(created);
+    }
+
+    @DeleteMapping("/{id}")
+    @RequirePermission(Permission.ADMIN_USER)
+    public ResponseEntity<Void> revokeInvite(@PathVariable UUID id) {
+        inviteService.revokeInvite(id);
+        return ResponseEntity.noContent().build();
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/controller/NotificationController.java

@@ -100,6 +100,6 @@ public class NotificationController {
     // ─── private helpers ──────────────────────────────────────────────────────
 
     private AppUser resolveUser(Authentication authentication) {
-        return userService.findByUsername(authentication.getName());
+        return userService.findByEmail(authentication.getName());
     }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/OcrController.java

@@ -4,7 +4,10 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.raddatz.familienarchiv.dto.BatchOcrDTO;
 import org.raddatz.familienarchiv.dto.OcrStatusDTO;
+import org.raddatz.familienarchiv.dto.TrainingHistoryResponse;
+import org.raddatz.familienarchiv.dto.TrainingInfoResponse;
 import org.raddatz.familienarchiv.dto.TriggerOcrDTO;
+import org.raddatz.familienarchiv.dto.TriggerSenderTrainingDTO;
 import org.raddatz.familienarchiv.model.AppUser;
 import org.raddatz.familienarchiv.model.OcrJob;
 import org.raddatz.familienarchiv.model.OcrTrainingRun;
@@ -15,6 +18,7 @@ import org.raddatz.familienarchiv.service.OcrProgressService;
 import org.raddatz.familienarchiv.service.OcrService;
 import org.raddatz.familienarchiv.service.OcrTrainingService;
 import org.raddatz.familienarchiv.service.SegmentationTrainingExportService;
+import org.raddatz.familienarchiv.service.SenderModelService;
 import org.raddatz.familienarchiv.service.TrainingDataExportService;
 import org.raddatz.familienarchiv.service.UserService;
 import org.springframework.http.HttpHeaders;
@@ -42,6 +46,7 @@ public class OcrController {
     private final TrainingDataExportService trainingDataExportService;
     private final SegmentationTrainingExportService segmentationTrainingExportService;
     private final OcrTrainingService ocrTrainingService;
+    private final SenderModelService senderModelService;
 
     @PostMapping("/api/documents/{documentId}/ocr")
     @ResponseStatus(HttpStatus.ACCEPTED)
@@ -130,14 +135,33 @@ public class OcrController {
 
     @GetMapping("/api/ocr/training-info")
     @RequirePermission(Permission.ADMIN)
-    public OcrTrainingService.TrainingInfoResponse getTrainingInfo() {
+    public TrainingInfoResponse getTrainingInfo() {
         return ocrTrainingService.getTrainingInfo();
     }
 
+    @GetMapping("/api/ocr/training-info/global")
+    @RequirePermission(Permission.ADMIN)
+    public TrainingHistoryResponse getGlobalTrainingHistory() {
+        return ocrTrainingService.getGlobalTrainingHistory();
+    }
+
+    @GetMapping("/api/ocr/training-info/{personId}")
+    @RequirePermission(Permission.ADMIN)
+    public TrainingHistoryResponse getSenderTrainingHistory(@PathVariable UUID personId) {
+        return ocrTrainingService.getSenderTrainingHistory(personId);
+    }
+
+    @PostMapping("/api/ocr/train-sender")
+    @ResponseStatus(HttpStatus.ACCEPTED)
+    @RequirePermission(Permission.ADMIN)
+    public OcrTrainingRun triggerSenderTraining(@Valid @RequestBody TriggerSenderTrainingDTO dto) {
+        return senderModelService.triggerManualSenderTraining(dto.personId());
+    }
+
     private UUID resolveUserId(Authentication authentication) {
         if (authentication == null || !authentication.isAuthenticated()) return null;
         try {
-            AppUser user = userService.findByUsername(authentication.getName());
+            AppUser user = userService.findByEmail(authentication.getName());
             return user != null ? user.getId() : null;
         } catch (Exception e) {
             log.warn("Failed to resolve user ID for authentication: {}", authentication.getName(), e);

backend/src/main/java/org/raddatz/familienarchiv/controller/TagController.java

@@ -1,23 +1,29 @@
 package org.raddatz.familienarchiv.controller;
 
 import java.util.List;
-import java.util.Map;
 import java.util.UUID;
 
+import org.raddatz.familienarchiv.dto.MergeTagDTO;
+import org.raddatz.familienarchiv.dto.TagTreeNodeDTO;
+import org.raddatz.familienarchiv.dto.TagUpdateDTO;
 import org.raddatz.familienarchiv.model.Tag;
 import org.raddatz.familienarchiv.security.Permission;
 import org.raddatz.familienarchiv.security.RequirePermission;
 import org.raddatz.familienarchiv.service.DocumentService;
 import org.raddatz.familienarchiv.service.TagService;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.bind.annotation.RestController;
+import jakarta.validation.Valid;
 
 import lombok.RequiredArgsConstructor;
 
@@ -31,8 +37,8 @@ public class TagController {
 
     @PutMapping("/{id}")
     @RequirePermission(Permission.ADMIN_TAG)
-    public ResponseEntity<Tag> updateTag(@PathVariable UUID id, @RequestBody Map<String, String> payload) {
-        return ResponseEntity.ok(tagService.update(id, payload.get("name")));
+    public ResponseEntity<Tag> updateTag(@PathVariable UUID id, @RequestBody TagUpdateDTO dto) {
+        return ResponseEntity.ok(tagService.update(id, dto));
     }
 
     @DeleteMapping("/{id}")
@@ -46,4 +52,22 @@ public class TagController {
     public List<Tag> searchTags(@RequestParam(defaultValue = "") String query) {
         return tagService.search(query);
     }
+
+    @GetMapping("/tree")
+    public List<TagTreeNodeDTO> getTagTree() {
+        return tagService.getTagTree();
+    }
+
+    @PostMapping("/{id}/merge")
+    @RequirePermission(Permission.ADMIN_TAG)
+    public ResponseEntity<Tag> mergeTag(@PathVariable UUID id, @Valid @RequestBody MergeTagDTO dto) {
+        return ResponseEntity.ok(tagService.mergeTags(id, dto.targetId()));
+    }
+
+    @DeleteMapping("/{id}/subtree")
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    @RequirePermission(Permission.ADMIN_TAG)
+    public void deleteSubtree(@PathVariable UUID id) {
+        tagService.deleteWithDescendants(id);
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/TranscriptionBlockController.java

@@ -5,12 +5,11 @@ import lombok.extern.slf4j.Slf4j;
 import org.raddatz.familienarchiv.dto.CreateTranscriptionBlockDTO;
 import org.raddatz.familienarchiv.dto.ReorderTranscriptionBlocksDTO;
 import org.raddatz.familienarchiv.dto.UpdateTranscriptionBlockDTO;
-import org.raddatz.familienarchiv.exception.DomainException;
-import org.raddatz.familienarchiv.model.AppUser;
 import org.raddatz.familienarchiv.model.TranscriptionBlock;
 import org.raddatz.familienarchiv.model.TranscriptionBlockVersion;
 import org.raddatz.familienarchiv.security.Permission;
 import org.raddatz.familienarchiv.security.RequirePermission;
+import org.raddatz.familienarchiv.security.SecurityUtils;
 import org.raddatz.familienarchiv.service.TranscriptionService;
 import org.raddatz.familienarchiv.service.UserService;
 import org.springframework.http.HttpStatus;
@@ -85,8 +84,10 @@ public class TranscriptionBlockController {
     @RequirePermission(Permission.WRITE_ALL)
     public TranscriptionBlock reviewBlock(
             @PathVariable UUID documentId,
-            @PathVariable UUID blockId) {
-        return transcriptionService.reviewBlock(documentId, blockId);
+            @PathVariable UUID blockId,
+            Authentication authentication) {
+        UUID userId = requireUserId(authentication);
+        return transcriptionService.reviewBlock(documentId, blockId, userId);
     }
 
     @GetMapping("/{blockId}/history")
@@ -98,13 +99,6 @@ public class TranscriptionBlockController {
     }
 
     private UUID requireUserId(Authentication authentication) {
-        if (authentication == null || !authentication.isAuthenticated()) {
-            throw DomainException.unauthorized("Authentication required");
-        }
-        AppUser user = userService.findByUsername(authentication.getName());
-        if (user == null) {
-            throw DomainException.unauthorized("User not found");
-        }
-        return user.getId();
+        return SecurityUtils.requireUserId(authentication, userService);
     }
 }

backend/src/main/java/org/raddatz/familienarchiv/controller/TranscriptionQueueController.java

@@ -0,0 +1,47 @@
+package org.raddatz.familienarchiv.controller;
+
+import lombok.RequiredArgsConstructor;
+import org.raddatz.familienarchiv.dto.TranscriptionQueueItemDTO;
+import org.raddatz.familienarchiv.dto.TranscriptionWeeklyStatsDTO;
+import org.raddatz.familienarchiv.security.Permission;
+import org.raddatz.familienarchiv.security.RequirePermission;
+import org.raddatz.familienarchiv.service.TranscriptionQueueService;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+
+/**
+ * Serves the three Mission Control Strip columns for the dashboard.
+ * All endpoints require READ_ALL — same guard as the rest of the archive.
+ */
+@RestController
+@RequestMapping("/api/transcription")
+@RequiredArgsConstructor
+@RequirePermission(Permission.READ_ALL)
+public class TranscriptionQueueController {
+
+    private final TranscriptionQueueService transcriptionQueueService;
+
+    @GetMapping("/segmentation-queue")
+    public ResponseEntity<List<TranscriptionQueueItemDTO>> getSegmentationQueue() {
+        return ResponseEntity.ok(transcriptionQueueService.getSegmentationQueue());
+    }
+
+    @GetMapping("/transcription-queue")
+    public ResponseEntity<List<TranscriptionQueueItemDTO>> getTranscriptionQueue() {
+        return ResponseEntity.ok(transcriptionQueueService.getTranscriptionQueue());
+    }
+
+    @GetMapping("/ready-to-read")
+    public ResponseEntity<List<TranscriptionQueueItemDTO>> getReadyToRead() {
+        return ResponseEntity.ok(transcriptionQueueService.getReadyToReadQueue());
+    }
+
+    @GetMapping("/weekly-stats")
+    public ResponseEntity<TranscriptionWeeklyStatsDTO> getWeeklyStats() {
+        return ResponseEntity.ok(transcriptionQueueService.getWeeklyStats());
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/controller/UserController.java

@@ -4,6 +4,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.UUID;
 
+import jakarta.validation.Valid;
 import org.raddatz.familienarchiv.dto.AdminUpdateUserRequest;
 import org.raddatz.familienarchiv.dto.ChangePasswordDTO;
 import org.raddatz.familienarchiv.dto.CreateUserRequest;
@@ -38,7 +39,7 @@ public class UserController {
         if (authentication == null || !authentication.isAuthenticated()) {
             return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
         }
-        AppUser user = userService.findByUsername(authentication.getName());
+        AppUser user = userService.findByEmail(authentication.getName());
         user.setPassword(null);
         return ResponseEntity.ok(user);
     }
@@ -46,7 +47,7 @@ public class UserController {
     @PutMapping("users/me")
     public ResponseEntity<AppUser> updateProfile(Authentication authentication,
                                                   @RequestBody UpdateProfileDTO dto) {
-        AppUser current = userService.findByUsername(authentication.getName());
+        AppUser current = userService.findByEmail(authentication.getName());
         AppUser updated = userService.updateProfile(current.getId(), dto);
         updated.setPassword(null);
         return ResponseEntity.ok(updated);
@@ -56,7 +57,7 @@ public class UserController {
     @ResponseStatus(HttpStatus.NO_CONTENT)
     public void changePassword(Authentication authentication,
                                @RequestBody ChangePasswordDTO dto) {
-        AppUser current = userService.findByUsername(authentication.getName());
+        AppUser current = userService.findByEmail(authentication.getName());
         userService.changePassword(current.getId(), dto);
     }
 
@@ -77,7 +78,7 @@ public class UserController {
 
     @PostMapping("/users")
     @RequirePermission(Permission.ADMIN_USER)
-    public ResponseEntity<AppUser> createUser(@RequestBody CreateUserRequest request) {
+    public ResponseEntity<AppUser> createUser(@Valid @RequestBody CreateUserRequest request) {
         return ResponseEntity.ok(userService.createUserOrUpdate(request));
     }
 

backend/src/main/java/org/raddatz/familienarchiv/dashboard/ActivityFeedItemDTO.java

@@ -0,0 +1,33 @@
+package org.raddatz.familienarchiv.dashboard;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.annotation.Nullable;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+import org.raddatz.familienarchiv.audit.AuditKind;
+
+import java.time.OffsetDateTime;
+import java.util.UUID;
+
+public record ActivityFeedItemDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) AuditKind kind,
+        @Nullable ActivityActorDTO actor,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID documentId,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String documentTitle,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) OffsetDateTime happenedAt,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) boolean youMentioned,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) boolean youParticipated,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int count,
+        @Nullable OffsetDateTime happenedAtUntil,
+        @Nullable
+        @Schema(
+                requiredMode = Schema.RequiredMode.NOT_REQUIRED,
+                description = "Deep-link target comment; populated only for COMMENT_ADDED and MENTION_CREATED kinds."
+        )
+        UUID commentId,
+        @Nullable
+        @Schema(
+                requiredMode = Schema.RequiredMode.NOT_REQUIRED,
+                description = "Annotation associated with the comment; populated only for COMMENT_ADDED and MENTION_CREATED kinds."
+        )
+        UUID annotationId
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dashboard/DashboardController.java

@@ -0,0 +1,51 @@
+package org.raddatz.familienarchiv.dashboard;
+
+import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.media.ArraySchema;
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.RequiredArgsConstructor;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.security.Permission;
+import org.raddatz.familienarchiv.security.RequirePermission;
+import org.raddatz.familienarchiv.security.SecurityUtils;
+import org.raddatz.familienarchiv.service.UserService;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+
+@RestController
+@RequestMapping("/api/dashboard")
+@RequirePermission(Permission.READ_ALL)
+@RequiredArgsConstructor
+public class DashboardController {
+
+    private final DashboardService dashboardService;
+    private final UserService userService;
+
+    @GetMapping("/resume")
+    public DashboardResumeDTO getResume(Authentication authentication) {
+        UUID userId = SecurityUtils.requireUserId(authentication, userService);
+        return dashboardService.getResume(userId);
+    }
+
+    @GetMapping("/pulse")
+    public DashboardPulseDTO getPulse(Authentication authentication) {
+        UUID userId = SecurityUtils.requireUserId(authentication, userService);
+        return dashboardService.getPulse(userId);
+    }
+
+    @GetMapping("/activity")
+    public List<ActivityFeedItemDTO> getActivity(
+            Authentication authentication,
+            @RequestParam(defaultValue = "7") int limit,
+            @Parameter(description = "Filter by audit kinds; omit for all rollup-eligible kinds",
+                    array = @ArraySchema(schema = @Schema(implementation = AuditKind.class)))
+            @RequestParam(required = false) Set<AuditKind> kinds) {
+        UUID userId = SecurityUtils.requireUserId(authentication, userService);
+        Set<AuditKind> effectiveKinds = (kinds == null || kinds.isEmpty()) ? AuditKind.ROLLUP_ELIGIBLE : kinds;
+        return dashboardService.getActivity(userId, Math.min(limit, 40), effectiveKinds);
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/dashboard/DashboardPulseDTO.java

@@ -0,0 +1,15 @@
+package org.raddatz.familienarchiv.dashboard;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+
+import java.util.List;
+
+public record DashboardPulseDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int pages,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int annotated,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int transcribed,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int uploaded,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int yourPages,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) List<ActivityActorDTO> contributors
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dashboard/DashboardResumeDTO.java

@@ -0,0 +1,19 @@
+package org.raddatz.familienarchiv.dashboard;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.annotation.Nullable;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+
+import java.util.List;
+import java.util.UUID;
+
+public record DashboardResumeDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID documentId,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String title,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String caption,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String excerpt,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int totalBlocks,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int pct,
+        @Nullable String thumbnailUrl,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) List<ActivityActorDTO> collaborators
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dashboard/DashboardService.java

@@ -0,0 +1,203 @@
+package org.raddatz.familienarchiv.dashboard;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+import org.raddatz.familienarchiv.audit.ActivityFeedRow;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.audit.AuditLogQueryService;
+import org.raddatz.familienarchiv.audit.PulseStatsRow;
+import org.raddatz.familienarchiv.model.AppUser;
+import org.raddatz.familienarchiv.model.Document;
+import org.raddatz.familienarchiv.model.Person;
+import org.raddatz.familienarchiv.model.TranscriptionBlock;
+import org.raddatz.familienarchiv.service.CommentService;
+import org.raddatz.familienarchiv.service.DocumentService;
+import org.raddatz.familienarchiv.service.TranscriptionService;
+import org.raddatz.familienarchiv.service.UserService;
+import org.springframework.stereotype.Service;
+
+import java.time.DayOfWeek;
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+import java.time.temporal.TemporalAdjusters;
+import java.util.*;
+import java.util.stream.Stream;
+import java.util.stream.Collectors;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class DashboardService {
+
+    private final AuditLogQueryService auditLogQueryService;
+    private final DocumentService documentService;
+    private final TranscriptionService transcriptionService;
+    private final UserService userService;
+    private final CommentService commentService;
+
+    public DashboardResumeDTO getResume(UUID userId) {
+        Optional<UUID> docIdOpt = auditLogQueryService.findMostRecentDocumentForUser(userId);
+        if (docIdOpt.isEmpty()) return null;
+
+        UUID docId = docIdOpt.get();
+        Document doc;
+        try {
+            doc = documentService.getDocumentById(docId);
+        } catch (Exception e) {
+            log.warn("Resume: document {} not found for user {}", docId, userId);
+            return null;
+        }
+
+        List<TranscriptionBlock> blocks = transcriptionService.listBlocks(docId);
+        String excerpt = blocks.stream()
+                .filter(b -> b.getText() != null && !b.getText().isBlank())
+                .min(Comparator.comparingInt(TranscriptionBlock::getSortOrder))
+                .map(b -> b.getText().length() > 200 ? b.getText().substring(0, 200) + "…" : b.getText())
+                .orElse("");
+
+        int totalBlocks = blocks.size();
+        long reviewedBlocks = blocks.stream().filter(TranscriptionBlock::isReviewed).count();
+        int pct = totalBlocks > 0 ? (int) (reviewedBlocks * 100L / totalBlocks) : 0;
+
+        String caption = buildCaption(doc);
+
+        List<UUID> collaboratorIds = blocks.stream()
+                .map(TranscriptionBlock::getUpdatedBy)
+                .filter(Objects::nonNull)
+                .distinct()
+                .limit(5)
+                .toList();
+
+        List<ActivityActorDTO> collaborators = collaboratorIds.stream()
+                .map(uid -> {
+                    try {
+                        AppUser u = userService.getById(uid);
+                        return toActorDTO(u);
+                    } catch (Exception e) {
+                        return null;
+                    }
+                })
+                .filter(Objects::nonNull)
+                .toList();
+
+        return new DashboardResumeDTO(docId, doc.getTitle(), caption, excerpt,
+                totalBlocks, pct, doc.getThumbnailUrl(), collaborators);
+    }
+
+    public DashboardPulseDTO getPulse(UUID userId) {
+        OffsetDateTime weekStart = OffsetDateTime.now(ZoneOffset.UTC)
+                .with(TemporalAdjusters.previousOrSame(DayOfWeek.MONDAY))
+                .withHour(0).withMinute(0).withSecond(0).withNano(0);
+
+        PulseStatsRow stats = auditLogQueryService.getPulseStats(weekStart, userId);
+
+        List<ActivityFeedRow> feed = auditLogQueryService.findActivityFeed(userId, 50);
+        List<ActivityActorDTO> contributors = feed.stream()
+                .filter(r -> r.getActorId() != null)
+                .map(r -> new ActivityActorDTO(r.getActorInitials(), r.getActorColor(), r.getActorName()))
+                .filter(a -> !a.initials().isBlank())
+                .distinct()
+                .limit(6)
+                .toList();
+
+        return new DashboardPulseDTO(
+                (int) stats.getPages(),
+                (int) stats.getAnnotated(),
+                (int) stats.getTranscribed(),
+                (int) stats.getUploaded(),
+                (int) stats.getYourPages(),
+                contributors
+        );
+    }
+
+    public List<ActivityFeedItemDTO> getActivity(UUID currentUserId, int limit, Set<AuditKind> kinds) {
+        List<ActivityFeedRow> rows = auditLogQueryService.findActivityFeed(currentUserId, limit, kinds);
+
+        List<UUID> docIds = rows.stream()
+                .map(ActivityFeedRow::getDocumentId)
+                .filter(Objects::nonNull)
+                .distinct()
+                .toList();
+
+        Map<UUID, String> titleCache = new HashMap<>();
+        try {
+            documentService.getDocumentsByIds(docIds)
+                    .forEach(d -> titleCache.put(d.getId(), d.getTitle()));
+        } catch (Exception e) {
+            log.warn("Activity: failed to bulk-load document titles", e);
+        }
+
+        List<UUID> commentIds = rows.stream()
+                .map(ActivityFeedRow::getCommentId)
+                .filter(Objects::nonNull)
+                .distinct()
+                .toList();
+        Map<UUID, UUID> annotationByComment = commentIds.isEmpty()
+                ? Map.of()
+                : commentService.findAnnotationIdsByIds(commentIds);
+
+        return rows.stream().map(row -> {
+            ActivityActorDTO actor = row.getActorId() != null
+                    ? new ActivityActorDTO(row.getActorInitials(), row.getActorColor(), row.getActorName())
+                    : null;
+            String docTitle = titleCache.getOrDefault(row.getDocumentId(), "");
+            OffsetDateTime happenedAtUntil = row.getHappenedAtUntil() != null
+                    ? row.getHappenedAtUntil().atOffset(ZoneOffset.UTC)
+                    : null;
+            UUID commentId = row.getCommentId();
+            UUID annotationId = commentId != null ? annotationByComment.get(commentId) : null;
+            return new ActivityFeedItemDTO(
+                    org.raddatz.familienarchiv.audit.AuditKind.valueOf(row.getKind()),
+                    actor,
+                    row.getDocumentId(),
+                    docTitle,
+                    row.getHappenedAt().atOffset(ZoneOffset.UTC),
+                    row.isYouMentioned(),
+                    row.isYouParticipated(),
+                    row.getCount(),
+                    happenedAtUntil,
+                    commentId,
+                    annotationId
+            );
+        }).toList();
+    }
+
+    private String buildCaption(Document doc) {
+        StringBuilder sb = new StringBuilder();
+        if (doc.getSender() != null) sb.append(personName(doc.getSender()));
+        if (!doc.getReceivers().isEmpty()) {
+            String receivers = doc.getReceivers().stream()
+                    .map(this::personName).collect(Collectors.joining(", "));
+            if (!sb.isEmpty()) sb.append(" an ");
+            sb.append(receivers);
+        }
+        if (doc.getDocumentDate() != null) {
+            if (!sb.isEmpty()) sb.append(" · ");
+            sb.append(doc.getDocumentDate());
+        }
+        return sb.toString();
+    }
+
+    private String personName(Person p) {
+        if (p == null) return "";
+        if (p.getFirstName() != null && p.getLastName() != null) return p.getFirstName() + " " + p.getLastName();
+        if (p.getFirstName() != null) return p.getFirstName();
+        if (p.getLastName() != null) return p.getLastName();
+        return "";
+    }
+
+    private ActivityActorDTO toActorDTO(AppUser u) {
+        String initials = "";
+        if (u.getFirstName() != null && !u.getFirstName().isBlank())
+            initials += u.getFirstName().charAt(0);
+        if (u.getLastName() != null && !u.getLastName().isBlank())
+            initials += u.getLastName().charAt(0);
+        if (initials.isBlank() && u.getEmail() != null)
+            initials = u.getEmail().substring(0, 1).toUpperCase();
+        String fullName = Stream.of(u.getFirstName(), u.getLastName())
+                .filter(Objects::nonNull)
+                .collect(Collectors.joining(" "));
+        return new ActivityActorDTO(initials.toUpperCase(), u.getColor(), fullName);
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/BatchMetadataRequest.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.List;
+import java.util.UUID;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record BatchMetadataRequest(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) List<UUID> ids) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/BulkEditError.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.UUID;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record BulkEditError(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String message) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/BulkEditResult.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.List;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record BulkEditResult(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int updated,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) List<BulkEditError> errors) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/CreateInviteRequest.java

@@ -0,0 +1,18 @@
+package org.raddatz.familienarchiv.dto;
+
+import lombok.Data;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.UUID;
+
+@Data
+public class CreateInviteRequest {
+    private String label;
+    private Integer maxUses;
+    private String prefillFirstName;
+    private String prefillLastName;
+    private String prefillEmail;
+    private List<UUID> groupIds;
+    private LocalDateTime expiresAt;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/CreateUserRequest.java

@@ -1,6 +1,8 @@
 package org.raddatz.familienarchiv.dto;
 
-
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Pattern;
 import lombok.Data;
 
 import java.time.LocalDate;
@@ -9,7 +11,9 @@ import java.util.UUID;
 
 @Data
 public class CreateUserRequest {
-    private String username;
+    @NotBlank
+    @Email
+    @Pattern(regexp = "^[^:]+$", message = "Email must not contain a colon")
     private String email;
     private String initialPassword;
     private List<UUID> groupIds;

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentBatchMetadataDTO.java

@@ -0,0 +1,18 @@
+package org.raddatz.familienarchiv.dto;
+
+import lombok.Data;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+@Data
+public class DocumentBatchMetadataDTO {
+    private List<String> titles;
+    private UUID senderId;
+    private List<UUID> receiverIds;
+    private LocalDate documentDate;
+    private String location;
+    private List<String> tagNames;
+    private Boolean metadataComplete;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentBatchSummary.java

@@ -0,0 +1,10 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.UUID;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record DocumentBatchSummary(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String title,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String pdfUrl) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentBulkEditDTO.java

@@ -0,0 +1,60 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.List;
+import java.util.UUID;
+
+import jakarta.validation.constraints.Size;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * Request body for {@code PATCH /api/documents/bulk}. Field semantics:
+ * <ul>
+ *   <li>{@code tagNames} and {@code receiverIds} are <b>additive</b> —
+ *       merged into each document's existing set, never replacing it.</li>
+ *   <li>{@code senderId}, {@code documentLocation}, {@code archiveBox},
+ *       {@code archiveFolder} are <b>replace-on-non-blank</b> — null/blank
+ *       fields are skipped, anything else overwrites.</li>
+ * </ul>
+ *
+ * <p>Kept as a Lombok {@code @Data} POJO (not a record) for symmetry with
+ * the existing {@code DocumentUpdateDTO} and to keep test setup terse —
+ * the per-feature DTOs introduced alongside this one ({@link BulkEditError},
+ * {@link BulkEditResult}, {@link BatchMetadataRequest},
+ * {@link DocumentBatchSummary}) <i>are</i> records because they have no
+ * test-side mutation. Tracked in the cycle-1 review for follow-up.
+ *
+ * <p>Bean-validation caps below defend against payload-amplification: the
+ * 1 MiB SvelteKit proxy cap allows ~26k UUIDs through to the backend, and
+ * Jetty's default body limit is 8 MB. {@code @Size} guards catch malformed
+ * clients without depending on those outer bounds.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class DocumentBulkEditDTO {
+
+    // No @Size cap here on purpose: the controller's BULK_EDIT_MAX_IDS check
+    // returns the typed BULK_EDIT_TOO_MANY_IDS error code, which the frontend
+    // maps to a localised "Maximal 500 …" message via Paraglide. A bean-
+    // validation @Size would short-circuit that with a generic VALIDATION_ERROR.
+    private List<UUID> documentIds;
+
+    @Size(max = 200, message = "tagNames must not exceed 200 entries")
+    private List<@Size(max = 200, message = "tagName must not exceed 200 chars") String> tagNames;
+
+    private UUID senderId;
+
+    @Size(max = 200, message = "receiverIds must not exceed 200 entries")
+    private List<UUID> receiverIds;
+
+    @Size(max = 255, message = "documentLocation must not exceed 255 chars")
+    private String documentLocation;
+
+    @Size(max = 255, message = "archiveBox must not exceed 255 chars")
+    private String archiveBox;
+
+    @Size(max = 255, message = "archiveFolder must not exceed 255 chars")
+    private String archiveFolder;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentSearchItem.java

@@ -0,0 +1,18 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+import org.raddatz.familienarchiv.model.Document;
+
+import java.util.List;
+
+public record DocumentSearchItem(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        Document document,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        SearchMatchData matchData,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        int completionPercentage,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<ActivityActorDTO> contributors
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentSearchResult.java

@@ -1,16 +1,38 @@
 package org.raddatz.familienarchiv.dto;
 
-import org.raddatz.familienarchiv.model.Document;
+import io.swagger.v3.oas.annotations.media.Schema;
+import org.springframework.data.domain.Pageable;
 
 import java.util.List;
 
-public record DocumentSearchResult(List<Document> documents, long total) {
+public record DocumentSearchResult(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<DocumentSearchItem> items,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        long totalElements,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        int pageNumber,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        int pageSize,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        int totalPages
+) {
     /**
-     * Creates a result where total equals the list size.
-     * No pagination yet — the full matched set is always returned.
-     * When pagination is added, total must come from a DB COUNT query, not list.size().
+     * Single-page convenience factory used by empty-result shortcuts and by tests that
+     * don't care about paging. Treats the whole list as page 0 of itself.
      */
-    public static DocumentSearchResult of(List<Document> documents) {
-        return new DocumentSearchResult(documents, documents.size());
+    public static DocumentSearchResult of(List<DocumentSearchItem> items) {
+        int size = items.size();
+        return new DocumentSearchResult(items, size, 0, size, size == 0 ? 0 : 1);
+    }
+
+    /**
+     * Paged factory used by the service when it has a real Pageable + full match count
+     * (e.g. from Spring's Page<T> or from an in-memory sort-then-slice).
+     */
+    public static DocumentSearchResult paged(List<DocumentSearchItem> slice, Pageable pageable, long totalElements) {
+        int pageSize = pageable.getPageSize();
+        int totalPages = pageSize == 0 ? 0 : (int) ((totalElements + pageSize - 1) / pageSize);
+        return new DocumentSearchResult(slice, totalElements, pageable.getPageNumber(), pageSize, totalPages);
     }
 }

backend/src/main/java/org/raddatz/familienarchiv/dto/IncompleteDocumentDTO.java

@@ -2,9 +2,11 @@ package org.raddatz.familienarchiv.dto;
 
 import io.swagger.v3.oas.annotations.media.Schema;
 
+import java.time.LocalDateTime;
 import java.util.UUID;
 
 public record IncompleteDocumentDTO(
         @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
-        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String title
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String title,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) LocalDateTime uploadedAt
 ) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/InviteListItemDTO.java

@@ -0,0 +1,35 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+import java.util.UUID;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class InviteListItemDTO {
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID id;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String code;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String displayCode;
+    private String label;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private int useCount;
+    private Integer maxUses;
+    private LocalDateTime expiresAt;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private boolean revoked;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String status;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private LocalDateTime createdAt;
+    private String shareableUrl;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/InvitePrefillDTO.java

@@ -0,0 +1,18 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class InvitePrefillDTO {
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String firstName;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String lastName;
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String email;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/MatchOffset.java

@@ -0,0 +1,14 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+/**
+ * Character-level offset of a highlighted term within a text field.
+ * Offsets are Java {@code String} character positions (UTF-16 code units),
+ * which are identical to JavaScript string positions — consistent end-to-end
+ * for all German BMP characters (ä, ö, ü, ß, etc.).
+ */
+public record MatchOffset(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int start,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int length
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/MergeTagDTO.java

@@ -0,0 +1,6 @@
+package org.raddatz.familienarchiv.dto;
+
+import jakarta.validation.constraints.NotNull;
+import java.util.UUID;
+
+public record MergeTagDTO(@NotNull UUID targetId) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/RegisterRequest.java

@@ -0,0 +1,19 @@
+package org.raddatz.familienarchiv.dto;
+
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import lombok.Data;
+
+@Data
+public class RegisterRequest {
+    @NotBlank
+    private String code;
+    @NotBlank
+    @Email
+    private String email;
+    @NotBlank
+    private String password;
+    private String firstName;
+    private String lastName;
+    private boolean notifyOnMention = true;
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/SearchMatchData.java

@@ -0,0 +1,67 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * Match signals for a single document in a full-text search result.
+ * All fields are non-null except {@code transcriptionSnippet} and {@code summarySnippet},
+ * which are null when the respective field did not match the query.
+ */
+public record SearchMatchData(
+        /**
+         * Best-ranked matching transcription line, or null if no block matched.
+         */
+        String transcriptionSnippet,
+
+        /**
+         * Character offsets of highlighted terms within the document title.
+         * Empty when the title did not contribute to the match.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<MatchOffset> titleOffsets,
+
+        /**
+         * True when the sender's name matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        boolean senderMatched,
+
+        /**
+         * IDs of receiver persons whose names matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<UUID> matchedReceiverIds,
+
+        /**
+         * IDs of tags whose names matched the query.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<UUID> matchedTagIds,
+
+        /**
+         * Character offsets of highlighted terms within the transcription snippet.
+         * Empty when no transcription block matched or the snippet has no highlights.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<MatchOffset> snippetOffsets,
+
+        /**
+         * Highlighted summary excerpt, or null if the summary did not match the query.
+         */
+        String summarySnippet,
+
+        /**
+         * Character offsets of highlighted terms within the summary snippet.
+         * Empty when the summary did not match or has no highlights.
+         */
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        List<MatchOffset> summaryOffsets
+) {
+    /** Canonical "no match data" value for a single document. */
+    public static SearchMatchData empty() {
+        return new SearchMatchData(null, List.of(), false, List.of(), List.of(), List.of(), null, List.of());
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/TagOperator.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.dto;
+
+/** Determines how multiple selected tag filters are combined in a document search. */
+public enum TagOperator {
+    /** Every tag set must match (default). */
+    AND,
+    /** At least one tag set must match. */
+    OR
+}

backend/src/main/java/org/raddatz/familienarchiv/dto/TagTreeNodeDTO.java

@@ -0,0 +1,14 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.List;
+import java.util.UUID;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+public record TagTreeNodeDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String name,
+        String color,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int documentCount,
+        List<TagTreeNodeDTO> children,
+        @Schema(description = "Parent tag ID, null for root tags") UUID parentId) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TagUpdateDTO.java

@@ -0,0 +1,5 @@
+package org.raddatz.familienarchiv.dto;
+
+import java.util.UUID;
+
+public record TagUpdateDTO(String name, UUID parentId, String color) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TrainingHistoryResponse.java

@@ -0,0 +1,11 @@
+package org.raddatz.familienarchiv.dto;
+
+import org.raddatz.familienarchiv.model.OcrTrainingRun;
+
+import java.util.List;
+import java.util.Map;
+
+public record TrainingHistoryResponse(
+        List<OcrTrainingRun> runs,
+        Map<String, String> personNames
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TrainingInfoResponse.java

@@ -0,0 +1,19 @@
+package org.raddatz.familienarchiv.dto;
+
+import org.raddatz.familienarchiv.model.OcrTrainingRun;
+import org.raddatz.familienarchiv.model.SenderModel;
+
+import java.util.List;
+import java.util.Map;
+
+public record TrainingInfoResponse(
+        int availableBlocks,
+        int totalOcrBlocks,
+        int availableDocuments,
+        int availableSegBlocks,
+        boolean ocrServiceAvailable,
+        OcrTrainingRun lastRun,
+        List<OcrTrainingRun> runs,
+        Map<String, String> personNames,
+        List<SenderModel> senderModels
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TranscriptionQueueItemDTO.java

@@ -0,0 +1,19 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+public record TranscriptionQueueItemDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String title,
+        LocalDate documentDate,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int annotationCount,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int textedBlockCount,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int reviewedBlockCount,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) List<ActivityActorDTO> contributors,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) boolean hasMoreContributors
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TranscriptionWeeklyStatsDTO.java

@@ -0,0 +1,13 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+/**
+ * Weekly activity pulse for the Mission Control Strip column headers.
+ * Counts documents that received new work in each pipeline stage
+ * during the last 7 days.
+ */
+public record TranscriptionWeeklyStatsDTO(
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) long segmentationCount,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) long transcriptionCount
+) {}

backend/src/main/java/org/raddatz/familienarchiv/dto/TriggerSenderTrainingDTO.java

@@ -0,0 +1,12 @@
+package org.raddatz.familienarchiv.dto;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.validation.constraints.NotNull;
+
+import java.util.UUID;
+
+public record TriggerSenderTrainingDTO(
+        @NotNull
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+        UUID personId
+) {}

backend/src/main/java/org/raddatz/familienarchiv/exception/ErrorCode.java

@@ -38,6 +38,20 @@ public enum ErrorCode {
     /** A mass import is already in progress; only one can run at a time. 409 */
     IMPORT_ALREADY_RUNNING,
 
+    // --- Thumbnails ---
+    /** A thumbnail backfill is already in progress; only one can run at a time. 409 */
+    THUMBNAIL_BACKFILL_ALREADY_RUNNING,
+
+    // --- Invites ---
+    /** The invite code does not exist. 404 */
+    INVITE_NOT_FOUND,
+    /** The invite has already reached its use limit. 409 */
+    INVITE_EXHAUSTED,
+    /** The invite has been revoked by an admin. 409 */
+    INVITE_REVOKED,
+    /** The invite has passed its expiry date. 410 */
+    INVITE_EXPIRED,
+
     // --- Auth ---
     /** The request is not authenticated. 401 */
     UNAUTHORIZED,
@@ -77,10 +91,28 @@ public enum ErrorCode {
     OCR_PROCESSING_FAILED,
     /** A training run is already in progress. 409 */
     TRAINING_ALREADY_RUNNING,
+    /** Internal inconsistency: expected training run row was not found after creation. 500 */
+    OCR_TRAINING_CONFLICT,
+
+    // --- Tags ---
+    /** A tag with the given ID does not exist. 404 */
+    TAG_NOT_FOUND,
+    /** The supplied color token is not in the allowed palette. 400 */
+    INVALID_TAG_COLOR,
+    /** Setting this parent would create a cycle in the tag hierarchy. 400 */
+    TAG_CYCLE_DETECTED,
+    /** Merge source and target are the same tag. 400 */
+    TAG_MERGE_SELF,
+    /** The merge target is a descendant of the source tag. 400 */
+    TAG_MERGE_INVALID_TARGET,
 
     // --- Generic ---
     /** Request validation failed (missing or malformed fields). 400 */
     VALIDATION_ERROR,
+    /** Batch upload exceeds the maximum allowed file count per request. 400 */
+    BATCH_TOO_LARGE,
+    /** Bulk edit request exceeds the per-request document ID cap. 400 */
+    BULK_EDIT_TOO_MANY_IDS,
     /** An unexpected server-side error occurred. 500 */
     INTERNAL_ERROR,
 }

backend/src/main/java/org/raddatz/familienarchiv/model/AppUser.java

@@ -1,6 +1,9 @@
 package org.raddatz.familienarchiv.model;
 
 import jakarta.persistence.*;
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Pattern;
 import lombok.*;
 
 import org.hibernate.annotations.CreationTimestamp;
@@ -16,8 +19,12 @@ import java.util.HashSet;
 import java.util.Set;
 import java.util.UUID;
 
+import jakarta.persistence.PostLoad;
+import jakarta.persistence.PrePersist;
+import jakarta.persistence.PreUpdate;
+
 @Entity
-@Table(name = "users") // Tabellenname in Postgres
+@Table(name = "users")
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
@@ -30,26 +37,26 @@ public class AppUser {
     private UUID id;
 
     @Column(unique = true, nullable = false)
+    @NotBlank
+    @Email
+    @Pattern(regexp = "^[^:]+$", message = "Email must not contain a colon")
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
-    private String username;
+    private String email;
 
     @Column(nullable = false)
     @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
-    private String password; // Wird verschlüsselt gespeichert (BCrypt)
+    private String password;
 
     private String firstName;
     private String lastName;
     private LocalDate birthDate;
 
-    @Column(unique = true)
-    private String email;
-
     @Column(columnDefinition = "TEXT")
     private String contact;
 
     @Builder.Default
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
-    private boolean enabled = true; // Um User zu sperren ohne sie zu löschen
+    private boolean enabled = true;
 
     @Column(nullable = false)
     @Builder.Default
@@ -61,7 +68,6 @@ public class AppUser {
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private boolean notifyOnMention = false;
 
-    // Ein User kann in mehreren Gruppen sein
     @ManyToMany(fetch = FetchType.EAGER)
     @JoinTable(name = "users_groups", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "group_id"))
     @Builder.Default
@@ -72,31 +78,48 @@ public class AppUser {
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private LocalDateTime createdAt;
 
+    @Column(nullable = false)
+    @Builder.Default
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String color = "";
+
+    private static final String[] PALETTE = {
+        "#7a4f9a", "#5a8a6a", "#3060b0", "#a0522d", "#c0446e", "#c17a00", "#0e7490", "#1d4ed8"
+    };
+
+    public static String computeColor(UUID id) {
+        return PALETTE[Math.abs(id.hashCode()) % PALETTE.length];
+    }
+
+    @PrePersist
+    @PreUpdate
+    @PostLoad
+    void deriveColor() {
+        if (id != null && (color == null || color.isEmpty())) {
+            this.color = computeColor(id);
+        }
+    }
+
     public boolean hasPermission(String permission) {
         if (groups == null || groups.isEmpty()) {
             return false;
         }
         return this.groups.stream().anyMatch(group -> group.getPermissions().contains(permission));
-
     }
 
-public AppUser updateFromRequest(CreateUserRequest request, PasswordEncoder passwordEncoder, Set<UserGroup> groups) {
-    if (request.getUsername() != null && !request.getUsername().isBlank()) {
-        this.username = request.getUsername();
-    }
+    public AppUser updateFromRequest(CreateUserRequest request, PasswordEncoder passwordEncoder, Set<UserGroup> groups) {
+        if (request.getEmail() != null && !request.getEmail().isBlank()) {
+            this.email = request.getEmail();
+        }
 
-    if (request.getEmail() != null && !request.getEmail().isBlank()) {
-        this.email = request.getEmail();
-    }
+        if (request.getInitialPassword() != null && !request.getInitialPassword().isBlank()) {
+            this.password = passwordEncoder.encode(request.getInitialPassword());
+        }
 
-    if (request.getInitialPassword() != null && !request.getInitialPassword().isBlank()) {
-        this.password = passwordEncoder.encode(request.getInitialPassword());
-    }
+        if (groups != null && !groups.isEmpty()) {
+            this.groups = groups;
+        }
 
-    if (groups != null && !groups.isEmpty()) {
-        this.groups = groups;
+        return this;
     }
-
-    return this;
-}
 }

backend/src/main/java/org/raddatz/familienarchiv/model/Document.java

@@ -6,8 +6,11 @@ import org.hibernate.annotations.CreationTimestamp;
 import org.hibernate.annotations.UpdateTimestamp;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import io.swagger.v3.oas.annotations.media.Schema;
 
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.util.HashSet;
@@ -43,6 +46,20 @@ public class Document {
     @Column(name = "file_hash", length = 64)
     private String fileHash;
 
+    // S3 key of the generated thumbnail (e.g. "thumbnails/{docId}.jpg"); null until generated
+    @Column(name = "thumbnail_key")
+    private String thumbnailKey;
+
+    @Column(name = "thumbnail_generated_at")
+    private LocalDateTime thumbnailGeneratedAt;
+
+    @Enumerated(EnumType.STRING)
+    @Column(name = "thumbnail_aspect", length = 16)
+    private ThumbnailAspect thumbnailAspect;
+
+    @Column(name = "page_count")
+    private Integer pageCount;
+
     // Originaler Dateiname beim Upload (z.B. "Brief_Oma_1940.pdf")
     @Column(name = "original_filename", nullable = false)
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
@@ -117,4 +134,19 @@ public class Document {
     @Enumerated(EnumType.STRING)
     @Builder.Default
     private Set<TrainingLabel> trainingLabels = new HashSet<>();
+
+    // The `?v={thumbnailGeneratedAt}` cache-buster is load-bearing: the thumbnail
+    // endpoint sends `Cache-Control: private, max-age=31536000, immutable`
+    // (DocumentController.getDocumentThumbnail). `immutable` is only safe because
+    // this URL changes whenever the underlying file does. Dropping the query param
+    // would let browsers serve a stale thumbnail for a year after the file is
+    // replaced, and shared caches could leak one user's thumbnail to another
+    // (CWE-525).
+    @JsonProperty("thumbnailUrl")
+    public String getThumbnailUrl() {
+        if (thumbnailKey == null) return null;
+        String base = "/api/documents/" + id + "/thumbnail";
+        if (thumbnailGeneratedAt == null) return base;
+        return base + "?v=" + URLEncoder.encode(thumbnailGeneratedAt.toString(), StandardCharsets.UTF_8);
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/model/InviteToken.java

@@ -0,0 +1,76 @@
+package org.raddatz.familienarchiv.model;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.persistence.*;
+import lombok.*;
+import org.hibernate.annotations.CreationTimestamp;
+
+import java.time.LocalDateTime;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.UUID;
+
+@Entity
+@Table(name = "invite_tokens")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class InviteToken {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID id;
+
+    @Column(nullable = false, unique = true, length = 10)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String code;
+
+    private String label;
+
+    private Integer maxUses;
+
+    @Column(nullable = false)
+    @Builder.Default
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private int useCount = 0;
+
+    private String prefillFirstName;
+    private String prefillLastName;
+    private String prefillEmail;
+
+    @ElementCollection(fetch = FetchType.EAGER)
+    @CollectionTable(name = "invite_token_group_ids", joinColumns = @JoinColumn(name = "invite_token_id"))
+    @Column(name = "group_id")
+    @Builder.Default
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private Set<UUID> groupIds = new HashSet<>();
+
+    private LocalDateTime expiresAt;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "created_by", nullable = false)
+    private AppUser createdBy;
+
+    @CreationTimestamp
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private LocalDateTime createdAt;
+
+    @Column(nullable = false)
+    @Builder.Default
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private boolean revoked = false;
+
+    public boolean isExhausted() {
+        return maxUses != null && useCount >= maxUses;
+    }
+
+    public boolean isExpired() {
+        return expiresAt != null && expiresAt.isBefore(LocalDateTime.now());
+    }
+
+    public boolean isActive() {
+        return !revoked && !isExhausted() && !isExpired();
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/model/OcrTrainingRun.java

@@ -59,6 +59,9 @@ public class OcrTrainingRun {
     @Column(name = "triggered_by")
     private UUID triggeredBy;
 
+    @Column(name = "person_id")
+    private UUID personId;
+
     @CreationTimestamp
     @Column(name = "created_at", nullable = false, updatable = false)
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)

backend/src/main/java/org/raddatz/familienarchiv/model/SenderModel.java

@@ -0,0 +1,56 @@
+package org.raddatz.familienarchiv.model;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.persistence.*;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.hibernate.annotations.CreationTimestamp;
+import org.hibernate.annotations.UpdateTimestamp;
+
+import java.time.Instant;
+import java.util.UUID;
+
+@Entity
+@Table(name = "sender_models")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class SenderModel {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID id;
+
+    @Column(name = "person_id", nullable = false, unique = true)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID personId;
+
+    @JsonIgnore
+    @Column(name = "model_path", nullable = false)
+    private String modelPath;
+
+    @Column
+    private Double accuracy;
+
+    @Column
+    private Double cer;
+
+    @Column(name = "corrected_lines_at_training", nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private int correctedLinesAtTraining;
+
+    @CreationTimestamp
+    @Column(name = "created_at", nullable = false, updatable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private Instant createdAt;
+
+    @UpdateTimestamp
+    @Column(name = "updated_at", nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private Instant updatedAt;
+}

backend/src/main/java/org/raddatz/familienarchiv/model/Tag.java

@@ -20,4 +20,11 @@ public class Tag {
     @Column(unique = true, nullable = false)
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private String name;
+
+    /** UUID of the parent tag, or null for root-level tags. */
+    @Column(name = "parent_id")
+    private UUID parentId;
+
+    /** Color token name (e.g. "sage"), only set on root-level tags. Null means no color. */
+    private String color;
 }

backend/src/main/java/org/raddatz/familienarchiv/model/ThumbnailAspect.java

@@ -0,0 +1,6 @@
+package org.raddatz.familienarchiv.model;
+
+public enum ThumbnailAspect {
+    PORTRAIT,
+    LANDSCAPE
+}

backend/src/main/java/org/raddatz/familienarchiv/model/TrainingStatus.java

@@ -1,6 +1,7 @@
 package org.raddatz.familienarchiv.model;
 
 public enum TrainingStatus {
+    QUEUED,
     RUNNING,
     DONE,
     FAILED

backend/src/main/java/org/raddatz/familienarchiv/repository/AppUserRepository.java

@@ -13,11 +13,10 @@ import java.util.UUID;
 
 @Repository
 public interface AppUserRepository extends JpaRepository<AppUser, UUID> {
-    Optional<AppUser> findByUsername(String username);
     Optional<AppUser> findByEmail(String email);
 
     @Query("SELECT u FROM AppUser u WHERE " +
-            "LOWER(COALESCE(u.firstName, '') || ' ' || COALESCE(u.lastName, '')) LIKE LOWER(CONCAT('%', :q, '%')) " +
-            "OR LOWER(u.username) LIKE LOWER(CONCAT('%', :q, '%'))")
-    List<AppUser> searchByNameOrUsername(@Param("q") String q, Pageable pageable);
-}
+            "LOWER(u.email) LIKE LOWER(CONCAT('%', :q, '%')) " +
+            "OR LOWER(COALESCE(u.firstName, '') || ' ' || COALESCE(u.lastName, '')) LIKE LOWER(CONCAT('%', :q, '%'))")
+    List<AppUser> searchByEmailOrName(@Param("q") String q, Pageable pageable);
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/CommentRepository.java

@@ -8,10 +8,6 @@ import java.util.UUID;
 
 public interface CommentRepository extends JpaRepository<DocumentComment, UUID> {
 
-    List<DocumentComment> findByDocumentIdAndAnnotationIdIsNullAndParentIdIsNull(UUID documentId);
-
-    List<DocumentComment> findByAnnotationIdAndParentIdIsNull(UUID annotationId);
-
     List<DocumentComment> findByParentId(UUID parentId);
 
     List<DocumentComment> findByBlockIdAndParentIdIsNull(UUID blockId);

backend/src/main/java/org/raddatz/familienarchiv/repository/CompletionStatsRow.java

@@ -0,0 +1,8 @@
+package org.raddatz.familienarchiv.repository;
+
+import java.util.UUID;
+
+public interface CompletionStatsRow {
+    UUID getDocumentId();
+    int getCompletionPercentage();
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/DocumentRepository.java

@@ -46,6 +46,8 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
 
     List<Document> findByFileHashIsNullAndFilePathIsNotNull();
 
+    List<Document> findByFilePathIsNotNullAndThumbnailKeyIsNull();
+
     @Query("SELECT d.id, d.title FROM Document d WHERE d.id IN :ids")
     List<Object[]> findIdAndTitleByIdIn(@Param("ids") Collection<UUID> ids);
 
@@ -83,10 +85,157 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
 
     @Query(nativeQuery = true, value = """
             SELECT d.id FROM documents d
-            WHERE d.search_vector @@ websearch_to_tsquery('german', :query)
-            ORDER BY ts_rank(d.search_vector, websearch_to_tsquery('german', :query)) DESC,
+            CROSS JOIN LATERAL (
+                SELECT CASE WHEN websearch_to_tsquery('german', :query)::text <> ''
+                            THEN to_tsquery('german', regexp_replace(
+                                     websearch_to_tsquery('german', :query)::text,
+                                     '''([^'']+)''',
+                                     '''\\1'':*',
+                                     'g'))
+                       END AS pq
+            ) q
+            WHERE d.search_vector @@ q.pq
+            ORDER BY ts_rank(d.search_vector, q.pq) DESC,
                      d.meta_date DESC NULLS LAST
             """)
     List<UUID> findRankedIdsByFts(@Param("query") String query);
 
+    /**
+     * Returns match-enrichment data for a set of documents identified by their IDs.
+     * Each row contains (in column order):
+     * <ol>
+     *   <li>UUID   — document id</li>
+     *   <li>String — title headline with \x01/\x02 delimiters around matched terms</li>
+     *   <li>String — best-ranked transcription snippet with \x01/\x02 delimiters, or null</li>
+     *   <li>Boolean — whether the sender's name matched the query</li>
+     *   <li>String — comma-separated matched receiver UUIDs, or null</li>
+     *   <li>String — comma-separated matched tag UUIDs, or null</li>
+     *   <li>String — summary snippet with \x01/\x02 delimiters, or null if summary didn't match</li>
+     * </ol>
+     * Short-circuit before calling this method when {@code ids} is empty or {@code query} is blank.
+     */
+    @Query(nativeQuery = true, value = """
+            SELECT
+                d.id,
+                ts_headline('german', d.title, q.pq,
+                    'StartSel=' || chr(1) || ',StopSel=' || chr(2) || ',HighlightAll=true')
+                    AS title_headline,
+                CASE WHEN best_block.text IS NOT NULL THEN
+                    ts_headline('german', best_block.text, q.pq,
+                        'StartSel=' || chr(1) || ',StopSel=' || chr(2) || ',MaxWords=50,MinWords=20')
+                END AS transcription_snippet,
+                (s.id IS NOT NULL AND
+                 to_tsvector('german', COALESCE(s.first_name, '') || ' ' || COALESCE(s.last_name, ''))
+                     @@ q.pq)
+                    AS sender_matched,
+                (SELECT string_agg(r.id::text, ',')
+                 FROM document_receivers dr
+                 JOIN persons r ON r.id = dr.person_id
+                 WHERE dr.document_id = d.id
+                   AND to_tsvector('german', COALESCE(r.first_name, '') || ' ' || r.last_name)
+                           @@ q.pq
+                ) AS matched_receiver_ids,
+                (SELECT string_agg(t.id::text, ',')
+                 FROM document_tags dt
+                 JOIN tag t ON t.id = dt.tag_id
+                 WHERE dt.document_id = d.id
+                   AND to_tsvector('german', t.name) @@ q.pq
+                ) AS matched_tag_ids,
+                CASE WHEN d.summary IS NOT NULL AND d.summary <> ''
+                          AND to_tsvector('german', d.summary) @@ q.pq
+                     THEN ts_headline('german', d.summary, q.pq,
+                              'StartSel=' || chr(1) || ',StopSel=' || chr(2) || ',MaxWords=50,MinWords=20')
+                END AS summary_snippet
+            FROM documents d
+            CROSS JOIN LATERAL (
+                SELECT CASE WHEN websearch_to_tsquery('german', :query)::text <> ''
+                            THEN to_tsquery('german', regexp_replace(
+                                     websearch_to_tsquery('german', :query)::text,
+                                     '''([^'']+)''',
+                                     '''\\1'':*',
+                                     'g'))
+                       END AS pq
+            ) q
+            LEFT JOIN persons s ON s.id = d.sender_id
+            LEFT JOIN LATERAL (
+                SELECT tb.text
+                FROM transcription_blocks tb
+                WHERE tb.document_id = d.id
+                  AND to_tsvector('german', tb.text) @@ q.pq
+                ORDER BY ts_rank(to_tsvector('german', tb.text), q.pq) DESC
+                LIMIT 1
+            ) best_block ON true
+            WHERE d.id IN :ids
+            """)
+    List<Object[]> findEnrichmentData(@Param("ids") Collection<UUID> ids, @Param("query") String query);
+
+    // --- Mission Control Strip queues ---
+
+    /** Documents with no annotations — Segmentierung column. */
+    @Query(nativeQuery = true, value = """
+            SELECT d.id, d.title, d.meta_date AS documentDate,
+                   0 AS annotationCount, 0 AS textedBlockCount, 0 AS reviewedBlockCount
+            FROM documents d
+            WHERE d.status NOT IN ('PLACEHOLDER')
+              AND NOT EXISTS (SELECT 1 FROM document_annotations da WHERE da.document_id = d.id)
+            ORDER BY HASHTEXT(d.id::text || EXTRACT(WEEK FROM NOW())::int::text)
+            LIMIT :limit
+            """)
+    List<TranscriptionQueueProjection> findSegmentationQueue(@Param("limit") int limit);
+
+    /** Documents with annotations but not yet fully reviewed — Transkription column. */
+    @Query(nativeQuery = true, value = """
+            SELECT d.id, d.title, d.meta_date AS documentDate,
+                   COUNT(DISTINCT da.id)                                                             AS annotationCount,
+                   COUNT(DISTINCT CASE WHEN tb.text IS NOT NULL AND tb.text <> '' THEN tb.id END)   AS textedBlockCount,
+                   COUNT(DISTINCT CASE WHEN tb.reviewed = true THEN tb.id END)                      AS reviewedBlockCount
+            FROM documents d
+            JOIN document_annotations da ON da.document_id = d.id
+            LEFT JOIN transcription_blocks tb ON tb.document_id = d.id
+            GROUP BY d.id, d.title, d.meta_date
+            HAVING COUNT(DISTINCT da.id) > 0
+               AND (
+                 COUNT(DISTINCT CASE WHEN tb.reviewed = true THEN tb.id END)::float /
+                 COUNT(DISTINCT da.id)
+               ) < 0.90
+            ORDER BY COUNT(DISTINCT CASE WHEN tb.text IS NOT NULL AND tb.text <> '' THEN tb.id END) DESC,
+                     HASHTEXT(d.id::text || EXTRACT(WEEK FROM NOW())::int::text)
+            LIMIT :limit
+            """)
+    List<TranscriptionQueueProjection> findTranscriptionQueue(@Param("limit") int limit);
+
+    /** Documents with reviewed_pct >= 90 % — Lesefertig column. */
+    @Query(nativeQuery = true, value = """
+            SELECT d.id, d.title, d.meta_date AS documentDate,
+                   COUNT(DISTINCT da.id)                                                             AS annotationCount,
+                   COUNT(DISTINCT CASE WHEN tb.text IS NOT NULL AND tb.text <> '' THEN tb.id END)   AS textedBlockCount,
+                   COUNT(DISTINCT CASE WHEN tb.reviewed = true THEN tb.id END)                      AS reviewedBlockCount
+            FROM documents d
+            JOIN document_annotations da ON da.document_id = d.id
+            LEFT JOIN transcription_blocks tb ON tb.document_id = d.id
+            GROUP BY d.id, d.title, d.meta_date
+            HAVING COUNT(DISTINCT da.id) > 0
+               AND (
+                 COUNT(DISTINCT CASE WHEN tb.reviewed = true THEN tb.id END)::float /
+                 COUNT(DISTINCT da.id)
+               ) >= 0.90
+            ORDER BY (
+                COUNT(DISTINCT CASE WHEN tb.reviewed = true THEN tb.id END)::float /
+                COUNT(DISTINCT da.id)
+              ) DESC
+            LIMIT :limit
+            """)
+    List<TranscriptionQueueProjection> findReadyToReadQueue(@Param("limit") int limit);
+
+    /** Weekly pulse: distinct documents that received new work in each pipeline stage. */
+    @Query(nativeQuery = true, value = """
+            SELECT
+              (SELECT COUNT(DISTINCT da.document_id) FROM document_annotations da
+               WHERE da.created_at >= NOW() - INTERVAL '7 days')                             AS segmentationCount,
+              (SELECT COUNT(DISTINCT tb.document_id) FROM transcription_blocks tb
+               WHERE tb.created_at >= NOW() - INTERVAL '7 days'
+                 AND tb.text IS NOT NULL AND tb.text <> '')                                  AS transcriptionCount
+            """)
+    TranscriptionWeeklyStatsProjection findWeeklyStats();
+
 }

backend/src/main/java/org/raddatz/familienarchiv/repository/DocumentSpecifications.java

@@ -4,6 +4,7 @@ import jakarta.persistence.criteria.*;
 import java.time.LocalDate;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Set;
 import java.util.UUID;
 
 import org.raddatz.familienarchiv.model.Document;
@@ -54,34 +55,64 @@ public class DocumentSpecifications {
         return (root, query, cb) -> status == null ? null : cb.equal(root.get("status"), status);
     }
 
-    // Filtert nach Schlagworten (UND-Verknüpfung, exakter Match)
-    public static Specification<Document> hasTags(List<String> tags) {
+    /**
+     * Filtert nach vorausgeweiteten Tag-ID-Sets mit AND- oder OR-Logik.
+     *
+     * <p>AND (useOr=false): Das Dokument muss mindestens einen Tag aus <em>jedem</em> Set besitzen.
+     * <p>OR (useOr=true): Das Dokument muss mindestens einen Tag aus der Vereinigung aller Sets besitzen.
+     *
+     * <p>Jedes Set repräsentiert einen ausgewählten Tag inklusive aller seiner Nachkommen
+     * (vorausgeweitet durch {@code TagRepository.findDescendantIdsByName}).
+     */
+    public static Specification<Document> hasTags(List<Set<UUID>> tagIdSets, boolean useOr) {
         return (root, query, cb) -> {
-            if (tags == null || tags.isEmpty())
+            if (tagIdSets == null || tagIdSets.isEmpty())
                 return null;
 
-            List<Predicate> predicates = new ArrayList<>();
-
-            for (String tagName : tags) {
-                if (!StringUtils.hasText(tagName)) continue;
-
-                Subquery<Long> subquery = query.subquery(Long.class);
-                Root<Document> subRoot = subquery.from(Document.class);
-                Join<Document, Tag> subTags = subRoot.join("tags");
-
-                subquery.select(subRoot.get("id"))
-                        .where(
-                                cb.equal(subRoot.get("id"), root.get("id")),
-                                cb.equal(cb.lower(subTags.get("name")), tagName.trim().toLowerCase())
-                        );
-
-                predicates.add(cb.exists(subquery));
+            if (!useOr) {
+                // AND mode: an empty set means the tag resolved to no IDs (doesn't exist) —
+                // no document can satisfy the condition, so return no results immediately.
+                boolean hasEmptySet = tagIdSets.stream().anyMatch(s -> s == null || s.isEmpty());
+                if (hasEmptySet) return cb.disjunction();
             }
 
+            List<Set<UUID>> nonEmpty = tagIdSets.stream()
+                    .filter(s -> s != null && !s.isEmpty())
+                    .toList();
+            if (nonEmpty.isEmpty()) return null;
+
+            if (useOr) {
+                Set<UUID> union = new java.util.HashSet<>();
+                nonEmpty.forEach(union::addAll);
+                return documentHasTagIn(root, query, cb, union);
+            }
+
+            // AND: one EXISTS subquery per set
+            List<Predicate> predicates = new ArrayList<>();
+            for (Set<UUID> ids : nonEmpty) {
+                predicates.add(documentHasTagIn(root, query, cb, ids));
+            }
             return cb.and(predicates.toArray(new Predicate[0]));
         };
     }
 
+    private static Predicate documentHasTagIn(
+            Root<Document> root,
+            jakarta.persistence.criteria.CriteriaQuery<?> query,
+            jakarta.persistence.criteria.CriteriaBuilder cb,
+            Set<UUID> tagIds) {
+        Subquery<UUID> subquery = query.subquery(UUID.class);
+        Root<Document> subRoot = subquery.from(Document.class);
+        Join<Document, Tag> subTags = subRoot.join("tags");
+
+        subquery.select(subRoot.get("id"))
+                .where(
+                        cb.equal(subRoot.get("id"), root.get("id")),
+                        subTags.get("id").in(tagIds)
+                );
+        return cb.exists(subquery);
+    }
+
     // Filtert nach partiellem Tag-Namen (ILIKE) — für Live-Tag-Suche
     public static Specification<Document> hasTagPartial(String tagQ) {
         return (root, query, cb) -> {

backend/src/main/java/org/raddatz/familienarchiv/repository/InviteTokenRepository.java

@@ -0,0 +1,27 @@
+package org.raddatz.familienarchiv.repository;
+
+import jakarta.persistence.LockModeType;
+import org.raddatz.familienarchiv.model.InviteToken;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.UUID;
+
+public interface InviteTokenRepository extends JpaRepository<InviteToken, UUID> {
+
+    Optional<InviteToken> findByCode(String code);
+
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("SELECT t FROM InviteToken t WHERE t.code = :code")
+    Optional<InviteToken> findByCodeForUpdate(@Param("code") String code);
+
+    @Query("SELECT t FROM InviteToken t WHERE t.revoked = false AND (t.expiresAt IS NULL OR t.expiresAt > CURRENT_TIMESTAMP) AND (t.maxUses IS NULL OR t.useCount < t.maxUses) ORDER BY t.createdAt DESC")
+    List<InviteToken> findActive();
+
+    @Query("SELECT t FROM InviteToken t ORDER BY t.createdAt DESC")
+    List<InviteToken> findAllOrderedByCreatedAt();
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/OcrTrainingRunRepository.java

@@ -12,5 +12,15 @@ public interface OcrTrainingRunRepository extends JpaRepository<OcrTrainingRun,
 
     Optional<OcrTrainingRun> findFirstByStatus(TrainingStatus status);
 
-    List<OcrTrainingRun> findTop10ByOrderByCreatedAtDesc();
+    Optional<OcrTrainingRun> findFirstByStatusOrderByCreatedAtAsc(TrainingStatus status);
+
+    Optional<OcrTrainingRun> findFirstByPersonIdAndStatus(UUID personId, TrainingStatus status);
+
+    boolean existsByPersonIdAndStatus(UUID personId, TrainingStatus status);
+
+    List<OcrTrainingRun> findTop20ByOrderByCreatedAtDesc();
+
+    List<OcrTrainingRun> findByPersonIdIsNullOrderByCreatedAtDesc();
+
+    List<OcrTrainingRun> findByPersonIdOrderByCreatedAtDesc(UUID personId);
 }

backend/src/main/java/org/raddatz/familienarchiv/repository/SenderModelRepository.java

@@ -0,0 +1,12 @@
+package org.raddatz.familienarchiv.repository;
+
+import org.raddatz.familienarchiv.model.SenderModel;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.Optional;
+import java.util.UUID;
+
+public interface SenderModelRepository extends JpaRepository<SenderModel, UUID> {
+
+    Optional<SenderModel> findByPersonId(UUID personId);
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/TagRepository.java

@@ -1,13 +1,126 @@
 package org.raddatz.familienarchiv.repository;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
 import java.util.UUID;
 
 import org.raddatz.familienarchiv.model.Tag;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Modifying;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 public interface TagRepository extends JpaRepository<Tag, UUID> {
+
+    /** Typed projection for document-count aggregation results. */
+    interface TagCount {
+        UUID getTagId();
+        Long getCount();
+    }
+
+
     Optional<Tag> findByNameIgnoreCase(String name);
+
     List<Tag> findByNameContainingIgnoreCase(String name);
-}
+
+    /**
+     * Returns the IDs of all ancestors of the given tag (parent, grandparent, …)
+     * via a recursive CTE. Used for cycle detection before assigning a new parent.
+     * Includes a depth guard of 50 levels to prevent runaway queries.
+     */
+    @Query(value = """
+            WITH RECURSIVE ancestors AS (
+                SELECT parent_id, 0 AS depth
+                FROM tag
+                WHERE id = :tagId AND parent_id IS NOT NULL
+                UNION ALL
+                SELECT t.parent_id, a.depth + 1
+                FROM tag t
+                JOIN ancestors a ON t.id = a.parent_id
+                WHERE t.parent_id IS NOT NULL AND a.depth < 50
+            )
+            SELECT parent_id FROM ancestors
+            """, nativeQuery = true)
+    List<UUID> findAncestorIds(@Param("tagId") UUID tagId);
+
+    /**
+     * Returns the IDs of the tag with the given name AND all of its descendants
+     * via a recursive CTE. Used to expand a selected tag to inclusive hierarchy results.
+     * Includes a depth guard of 50 levels to prevent runaway queries.
+     */
+    @Query(value = """
+            WITH RECURSIVE descendants AS (
+                SELECT id, 0 AS depth FROM tag WHERE LOWER(name) = LOWER(:name)
+                UNION ALL
+                SELECT t.id, d.depth + 1 FROM tag t
+                JOIN descendants d ON t.parent_id = d.id
+                WHERE d.depth < 50
+            )
+            SELECT id FROM descendants
+            """, nativeQuery = true)
+    List<UUID> findDescendantIdsByName(@Param("name") String name);
+
+    /**
+     * Returns the IDs of the tag with the given ID AND all of its descendants
+     * via a recursive CTE. Used for merge validation and subtree delete.
+     * Includes a depth guard of 50 levels to prevent runaway queries.
+     */
+    @Query(value = """
+            WITH RECURSIVE descendants AS (
+                SELECT id, 0 AS depth FROM tag WHERE id = :tagId
+                UNION ALL
+                SELECT t.id, d.depth + 1 FROM tag t
+                JOIN descendants d ON t.parent_id = d.id
+                WHERE d.depth < 50
+            )
+            SELECT id FROM descendants
+            """, nativeQuery = true)
+    List<UUID> findDescendantIds(@Param("tagId") UUID tagId);
+
+    /**
+     * Reassigns document_tags rows from source to target, skipping rows where
+     * the target tag is already present (to avoid PK conflicts).
+     */
+    @Modifying(clearAutomatically = true)
+    @Query(value = """
+            UPDATE document_tags
+            SET tag_id = :targetId
+            WHERE tag_id = :sourceId
+              AND NOT EXISTS (
+                SELECT 1 FROM document_tags d2
+                WHERE d2.document_id = document_tags.document_id
+                  AND d2.tag_id = :targetId
+              )
+            """, nativeQuery = true)
+    void reassignDocumentTags(@Param("sourceId") UUID sourceId, @Param("targetId") UUID targetId);
+
+    /**
+     * Removes all document_tags rows for the given tag.
+     */
+    @Modifying(clearAutomatically = true)
+    @Query(value = "DELETE FROM document_tags WHERE tag_id = :tagId", nativeQuery = true)
+    void deleteDocumentTagsByTagId(@Param("tagId") UUID tagId);
+
+    /**
+     * Removes all document_tags rows for the given collection of tag IDs.
+     * Caller must guard against an empty collection — PostgreSQL rejects IN ().
+     */
+    @Modifying(clearAutomatically = true)
+    @Query(value = "DELETE FROM document_tags WHERE tag_id IN :ids", nativeQuery = true)
+    void deleteDocumentTagsByTagIds(@Param("ids") Collection<UUID> ids);
+
+    /**
+     * Re-parents all direct children of sourceId to targetId.
+     */
+    @Modifying(clearAutomatically = true)
+    @Query(value = "UPDATE tag SET parent_id = :targetId WHERE parent_id = :sourceId", nativeQuery = true)
+    void reparentChildren(@Param("sourceId") UUID sourceId, @Param("targetId") UUID targetId);
+
+    /**
+     * Returns (tagId, count) pairs for all tags that appear in document_tags.
+     * Used to populate documentCount in the tag tree without N+1 queries.
+     */
+    @Query(value = "SELECT tag_id AS tagId, COUNT(*) AS count FROM document_tags GROUP BY tag_id", nativeQuery = true)
+    List<TagCount> findDocumentCountsPerTag();
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/TranscriptionBlockRepository.java

@@ -3,13 +3,26 @@ package org.raddatz.familienarchiv.repository;
 import org.raddatz.familienarchiv.model.TranscriptionBlock;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
 import java.util.UUID;
 
 public interface TranscriptionBlockRepository extends JpaRepository<TranscriptionBlock, UUID> {
 
+    @Query(value = """
+            SELECT
+                b.document_id                                                              AS documentId,
+                ROUND(COUNT(*) FILTER (WHERE b.reviewed = true) * 100.0 / COUNT(*))::int  AS completionPercentage
+            FROM transcription_blocks b
+            WHERE b.document_id IN :documentIds
+            GROUP BY b.document_id
+            """, nativeQuery = true)
+    List<CompletionStatsRow> findCompletionStatsForDocuments(
+            @Param("documentIds") Collection<UUID> documentIds);
+
     List<TranscriptionBlock> findByDocumentIdOrderBySortOrderAsc(UUID documentId);
 
     Optional<TranscriptionBlock> findByIdAndDocumentId(UUID id, UUID documentId);
@@ -37,4 +50,22 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
             AND 'KURRENT_SEGMENTATION' MEMBER OF d.trainingLabels
             """)
     List<TranscriptionBlock> findSegmentationBlocks();
+
+    @Query("""
+            SELECT COUNT(b) FROM TranscriptionBlock b
+            JOIN Document d ON d.id = b.documentId
+            WHERE b.source = 'MANUAL'
+            AND d.sender.id = :personId
+            AND d.scriptType = 'HANDWRITING_KURRENT'
+            """)
+    long countManualKurrentBlocksByPerson(@Param("personId") UUID personId);
+
+    @Query("""
+            SELECT b FROM TranscriptionBlock b
+            JOIN Document d ON d.id = b.documentId
+            WHERE b.source = 'MANUAL'
+            AND d.sender.id = :personId
+            AND d.scriptType = 'HANDWRITING_KURRENT'
+            """)
+    List<TranscriptionBlock> findManualKurrentBlocksByPerson(@Param("personId") UUID personId);
 }

backend/src/main/java/org/raddatz/familienarchiv/repository/TranscriptionQueueProjection.java

@@ -0,0 +1,17 @@
+package org.raddatz.familienarchiv.repository;
+
+import java.time.LocalDate;
+import java.util.UUID;
+
+/**
+ * Spring Data projection for a single row in one of the three Mission Control Strip queues.
+ * Column aliases in the native SQL queries must match these getter names exactly.
+ */
+public interface TranscriptionQueueProjection {
+    UUID getId();
+    String getTitle();
+    LocalDate getDocumentDate();
+    int getAnnotationCount();
+    int getTextedBlockCount();
+    int getReviewedBlockCount();
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/TranscriptionWeeklyStatsProjection.java

@@ -0,0 +1,10 @@
+package org.raddatz.familienarchiv.repository;
+
+/**
+ * Spring Data projection for the weekly activity pulse stats.
+ * Column aliases in the native SQL query must match these getter names exactly.
+ */
+public interface TranscriptionWeeklyStatsProjection {
+    long getSegmentationCount();
+    long getTranscriptionCount();
+}

backend/src/main/java/org/raddatz/familienarchiv/security/SecurityUtils.java

@@ -0,0 +1,24 @@
+package org.raddatz.familienarchiv.security;
+
+import org.raddatz.familienarchiv.exception.DomainException;
+import org.raddatz.familienarchiv.model.AppUser;
+import org.raddatz.familienarchiv.service.UserService;
+import org.springframework.security.core.Authentication;
+
+import java.util.UUID;
+
+public final class SecurityUtils {
+
+    private SecurityUtils() {}
+
+    public static UUID requireUserId(Authentication authentication, UserService userService) {
+        if (authentication == null || !authentication.isAuthenticated()) {
+            throw DomainException.unauthorized("Authentication required");
+        }
+        AppUser user = userService.findByEmail(authentication.getName());
+        if (user == null) {
+            throw DomainException.unauthorized("User not found");
+        }
+        return user.getId();
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/service/AnnotationService.java

@@ -2,6 +2,8 @@ package org.raddatz.familienarchiv.service;
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.audit.AuditService;
 import org.raddatz.familienarchiv.dto.CreateAnnotationDTO;
 import org.raddatz.familienarchiv.dto.UpdateAnnotationDTO;
 import org.raddatz.familienarchiv.exception.DomainException;
@@ -14,6 +16,7 @@ import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.util.List;
+import java.util.Map;
 import java.util.UUID;
 
 @Slf4j
@@ -23,6 +26,7 @@ public class AnnotationService {
 
     private final AnnotationRepository annotationRepository;
     private final TranscriptionBlockRepository blockRepository;
+    private final AuditService auditService;
 
     public List<DocumentAnnotation> listAnnotations(UUID documentId) {
         return annotationRepository.findByDocumentId(documentId);
@@ -42,7 +46,10 @@ public class AnnotationService {
                 .createdBy(userId)
                 .build();
 
-        return annotationRepository.save(annotation);
+        DocumentAnnotation saved = annotationRepository.save(annotation);
+        auditService.logAfterCommit(AuditKind.ANNOTATION_CREATED, userId, saved.getDocumentId(),
+                Map.of("pageNumber", saved.getPageNumber()));
+        return saved;
     }
 
     @Transactional

backend/src/main/java/org/raddatz/familienarchiv/service/CommentService.java

@@ -1,17 +1,23 @@
 package org.raddatz.familienarchiv.service;
 
 import lombok.RequiredArgsConstructor;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.audit.AuditService;
 import org.raddatz.familienarchiv.dto.MentionDTO;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
 import org.raddatz.familienarchiv.model.AppUser;
 import org.raddatz.familienarchiv.model.DocumentComment;
+import org.raddatz.familienarchiv.model.TranscriptionBlock;
 import org.raddatz.familienarchiv.repository.CommentRepository;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.Collection;
+import java.util.HashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
 
@@ -22,16 +28,16 @@ public class CommentService {
     private final CommentRepository commentRepository;
     private final UserService userService;
     private final NotificationService notificationService;
+    private final AuditService auditService;
+    private final TranscriptionService transcriptionService;
 
-    public List<DocumentComment> getCommentsForDocument(UUID documentId) {
-        List<DocumentComment> roots =
-                commentRepository.findByDocumentIdAndAnnotationIdIsNullAndParentIdIsNull(documentId);
-        return withRepliesAndMentions(roots);
-    }
-
-    public List<DocumentComment> getCommentsForAnnotation(UUID annotationId) {
-        List<DocumentComment> roots = commentRepository.findByAnnotationIdAndParentIdIsNull(annotationId);
-        return withRepliesAndMentions(roots);
+    public Map<UUID, UUID> findAnnotationIdsByIds(Collection<UUID> commentIds) {
+        if (commentIds == null || commentIds.isEmpty()) return Map.of();
+        Map<UUID, UUID> result = new HashMap<>();
+        for (DocumentComment c : commentRepository.findAllById(commentIds)) {
+            if (c.getAnnotationId() != null) result.put(c.getId(), c.getAnnotationId());
+        }
+        return result;
     }
 
     public List<DocumentComment> getCommentsForBlock(UUID blockId) {
@@ -42,9 +48,11 @@ public class CommentService {
     @Transactional
     public DocumentComment postBlockComment(UUID documentId, UUID blockId, String content,
                                             List<UUID> mentionedUserIds, AppUser author) {
+        TranscriptionBlock block = transcriptionService.getBlock(documentId, blockId);
         DocumentComment comment = DocumentComment.builder()
                 .documentId(documentId)
                 .blockId(blockId)
+                .annotationId(block.getAnnotationId())
                 .content(content)
                 .authorId(author.getId())
                 .authorName(resolveAuthorName(author))
@@ -53,23 +61,7 @@ public class CommentService {
         DocumentComment saved = commentRepository.save(comment);
         withMentionDTOs(saved);
         notificationService.notifyMentions(mentionedUserIds, saved);
-        return saved;
-    }
-
-    @Transactional
-    public DocumentComment postComment(UUID documentId, UUID annotationId, String content,
-                                       List<UUID> mentionedUserIds, AppUser author) {
-        DocumentComment comment = DocumentComment.builder()
-                .documentId(documentId)
-                .annotationId(annotationId)
-                .content(content)
-                .authorId(author.getId())
-                .authorName(resolveAuthorName(author))
-                .build();
-        saveMentions(comment, mentionedUserIds);
-        DocumentComment saved = commentRepository.save(comment);
-        withMentionDTOs(saved);
-        notificationService.notifyMentions(mentionedUserIds, saved);
+        logCommentPosted(author, documentId, saved, mentionedUserIds);
         return saved;
     }
 
@@ -101,6 +93,7 @@ public class CommentService {
         participantIds.remove(author.getId());
         notificationService.notifyReply(saved, participantIds);
         notificationService.notifyMentions(mentionedUserIds, saved);
+        logCommentPosted(author, documentId, saved, mentionedUserIds);
         return saved;
     }
 
@@ -171,11 +164,22 @@ public class CommentService {
                         ErrorCode.COMMENT_NOT_FOUND, "Comment not found: " + commentId));
     }
 
+    private void logCommentPosted(AppUser author, UUID documentId, DocumentComment saved, List<UUID> mentionedUserIds) {
+        UUID actorId = author != null ? author.getId() : null;
+        String commentId = saved.getId().toString();
+        auditService.logAfterCommit(AuditKind.COMMENT_ADDED, actorId, documentId, Map.of("commentId", commentId));
+        if (mentionedUserIds != null) {
+            mentionedUserIds.forEach(mentionedUserId ->
+                    auditService.logAfterCommit(AuditKind.MENTION_CREATED, actorId, documentId,
+                            Map.of("commentId", commentId, "mentionedUserId", mentionedUserId.toString())));
+        }
+    }
+
     private String resolveAuthorName(AppUser author) {
         String first = author.getFirstName();
         String last = author.getLastName();
         if ((first == null || first.isBlank()) && (last == null || last.isBlank())) {
-            return author.getUsername();
+            return author.getEmail();
         }
         return ((first != null ? first : "") + " " + (last != null ? last : "")).strip();
     }

backend/src/main/java/org/raddatz/familienarchiv/service/CustomUserDetailsService.java

@@ -29,24 +29,22 @@ public class CustomUserDetailsService implements UserDetailsService {
     private final AppUserRepository userRepository;
 
     @Override
-    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
-        AppUser appUser = userRepository.findByUsername(username)
-                .orElseThrow(() -> new UsernameNotFoundException("User nicht gefunden: " + username));
+    public UserDetails loadUserByUsername(String email) throws UsernameNotFoundException {
+        AppUser appUser = userRepository.findByEmail(email)
+                .orElseThrow(() -> new UsernameNotFoundException("User nicht gefunden: " + email));
 
-        // Collect all permissions from all groups; warn about any that don't match a known Permission enum value
         var authorities = appUser.getGroups().stream()
                 .flatMap(group -> group.getPermissions().stream())
                 .peek(p -> {
                     if (!KNOWN_PERMISSIONS.contains(p)) {
-                        log.warn("Unknown permission '{}' found in database for user '{}' — it will be granted but never matched by @RequirePermission", p, appUser.getUsername());
+                        log.warn("Unknown permission '{}' found in database for user '{}' — it will be granted but never matched by @RequirePermission", p, appUser.getEmail());
                     }
                 })
                 .map(SimpleGrantedAuthority::new)
                 .collect(Collectors.toSet());
 
-        // Rückgabe des Standard Spring Security User Objekts
         return new User(
-                appUser.getUsername(),
+                appUser.getEmail(),
                 appUser.getPassword(),
                 appUser.isEnabled(),
                 true, true, true,

backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java

@@ -3,17 +3,31 @@ package org.raddatz.familienarchiv.service;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
+import org.raddatz.familienarchiv.audit.ActivityActorDTO;
+import org.raddatz.familienarchiv.audit.AuditKind;
+import org.raddatz.familienarchiv.audit.AuditLogQueryService;
+import org.raddatz.familienarchiv.audit.AuditService;
+import org.raddatz.familienarchiv.dto.DocumentBatchMetadataDTO;
+import org.raddatz.familienarchiv.dto.DocumentBatchSummary;
+import org.raddatz.familienarchiv.dto.DocumentBulkEditDTO;
+import org.raddatz.familienarchiv.dto.DocumentSearchItem;
+import org.raddatz.familienarchiv.dto.DocumentSearchResult;
+import org.raddatz.familienarchiv.dto.DocumentSort;
 import org.raddatz.familienarchiv.dto.DocumentUpdateDTO;
 import org.raddatz.familienarchiv.dto.IncompleteDocumentDTO;
+import org.raddatz.familienarchiv.dto.MatchOffset;
+import org.raddatz.familienarchiv.dto.SearchMatchData;
+import org.raddatz.familienarchiv.dto.TagOperator;
 import org.raddatz.familienarchiv.model.Document;
-import org.raddatz.familienarchiv.dto.DocumentSort;
 import org.raddatz.familienarchiv.model.DocumentStatus;
 import org.raddatz.familienarchiv.model.ScriptType;
 import org.raddatz.familienarchiv.model.TrainingLabel;
 import org.raddatz.familienarchiv.model.Person;
 import org.raddatz.familienarchiv.model.Tag;
 import org.raddatz.familienarchiv.repository.DocumentRepository;
+import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jpa.domain.Specification;
 import org.raddatz.familienarchiv.exception.DomainException;
@@ -52,6 +66,10 @@ public class DocumentService {
     private final TagService tagService;
     private final DocumentVersionService documentVersionService;
     private final AnnotationService annotationService;
+    private final AuditService auditService;
+    private final TranscriptionBlockQueryService transcriptionBlockQueryService;
+    private final AuditLogQueryService auditLogQueryService;
+    private final ThumbnailAsyncRunner thumbnailAsyncRunner;
 
     public record StoreResult(Document document, boolean isNew) {}
 
@@ -71,7 +89,7 @@ public class DocumentService {
      * - Wenn NEIN: Erstellt neuen Eintrag — isNew = true.
      */
     @Transactional
-    public StoreResult storeDocument(MultipartFile file) throws IOException {
+    public StoreResult storeDocument(MultipartFile file, UUID actorId) throws IOException {
         String originalFilename = file.getOriginalFilename();
 
         // 1. Check for existing record (findFirst to survive duplicate filenames in the DB)
@@ -104,11 +122,63 @@ public class DocumentService {
         document.setFilePath(upload.s3Key());
         document.setFileHash(upload.fileHash());
         document.setContentType(file.getContentType());
-        if (document.getStatus() == DocumentStatus.PLACEHOLDER) {
+        boolean wasPlaceholder = document.getStatus() == DocumentStatus.PLACEHOLDER;
+        if (wasPlaceholder) {
             document.setStatus(DocumentStatus.UPLOADED);
         }
 
-        return new StoreResult(documentRepository.save(document), isNew);
+        Document saved = documentRepository.save(document);
+        if (wasPlaceholder) {
+            auditService.logAfterCommit(AuditKind.FILE_UPLOADED, actorId, saved.getId(), null);
+        }
+        thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
+        return new StoreResult(saved, isNew);
+    }
+
+    public void validateBatch(int fileCount, DocumentBatchMetadataDTO metadata) {
+        // 50-file hard cap keeps FormData requests at a manageable size and protects against runaway bulk uploads.
+        if (fileCount > 50) {
+            throw DomainException.badRequest(ErrorCode.BATCH_TOO_LARGE, "Batch exceeds maximum of 50 files per request");
+        }
+        if (metadata != null && metadata.getTitles() != null && metadata.getTitles().size() > fileCount) {
+            throw DomainException.badRequest(ErrorCode.VALIDATION_ERROR, "titles count must not exceed files count");
+        }
+    }
+
+    @Transactional
+    public StoreResult storeDocumentWithBatchMetadata(
+            MultipartFile file, DocumentBatchMetadataDTO metadata, int fileIndex, UUID actorId) throws IOException {
+        StoreResult base = storeDocument(file, actorId);
+        Document doc = applyBatchMetadata(base.document(), metadata, fileIndex);
+        return new StoreResult(documentRepository.save(doc), base.isNew());
+    }
+
+    private Document applyBatchMetadata(Document doc, DocumentBatchMetadataDTO metadata, int fileIndex) {
+        if (metadata.getTitles() != null && fileIndex < metadata.getTitles().size()) {
+            doc.setTitle(metadata.getTitles().get(fileIndex));
+        }
+        if (metadata.getSenderId() != null) {
+            doc.setSender(personService.getById(metadata.getSenderId()));
+        }
+        if (metadata.getReceiverIds() != null && !metadata.getReceiverIds().isEmpty()) {
+            doc.setReceivers(new HashSet<>(personService.getAllById(metadata.getReceiverIds())));
+        }
+        if (metadata.getDocumentDate() != null) {
+            doc.setDocumentDate(metadata.getDocumentDate());
+        }
+        if (metadata.getLocation() != null) {
+            doc.setLocation(metadata.getLocation());
+        }
+        if (metadata.getMetadataComplete() != null) {
+            doc.setMetadataComplete(metadata.getMetadataComplete());
+        }
+        if (metadata.getTagNames() != null && !metadata.getTagNames().isEmpty()) {
+            UUID docId = doc.getId();
+            updateDocumentTags(docId, metadata.getTagNames());
+            doc = documentRepository.findById(docId)
+                    .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Not found after batch metadata: " + docId));
+        }
+        return doc;
     }
 
     @Transactional
@@ -170,7 +240,8 @@ public class DocumentService {
         }
 
         // Datei
-        if (file != null && !file.isEmpty()) {
+        boolean fileUploaded = file != null && !file.isEmpty();
+        if (fileUploaded) {
             FileService.UploadResult upload = fileService.uploadFile(file, file.getOriginalFilename());
             doc.setFilePath(upload.s3Key());
             doc.setFileHash(upload.fileHash());
@@ -180,14 +251,19 @@ public class DocumentService {
 
         Document finalDoc = documentRepository.save(doc);
         documentVersionService.recordVersion(finalDoc);
+        if (fileUploaded) {
+            thumbnailAsyncRunner.dispatchAfterCommit(finalDoc.getId());
+        }
         return finalDoc;
     }
 
     @Transactional
-    public Document updateDocument(UUID id, DocumentUpdateDTO dto, MultipartFile newFile) throws IOException {
+    public Document updateDocument(UUID id, DocumentUpdateDTO dto, MultipartFile newFile, UUID actorId) throws IOException {
         Document doc = documentRepository.findById(id)
                 .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + id));
 
+        DocumentStatus statusBefore = doc.getStatus();
+
         // 1. Einfache Felder Update
         doc.setTitle(dto.getTitle());
         doc.setDocumentDate(dto.getDocumentDate());
@@ -230,7 +306,8 @@ public class DocumentService {
         }
 
         // 4. Datei austauschen (nur wenn eine neue ausgewählt wurde)
-        if (newFile != null && !newFile.isEmpty()) {
+        boolean fileReplaced = newFile != null && !newFile.isEmpty();
+        if (fileReplaced) {
             FileService.UploadResult upload = fileService.uploadFile(newFile, newFile.getOriginalFilename());
             doc.setFilePath(upload.s3Key());
             doc.setFileHash(upload.fileHash());
@@ -241,26 +318,161 @@ public class DocumentService {
 
         Document saved = documentRepository.save(doc);
         documentVersionService.recordVersion(saved);
+
+        if (saved.getStatus() != statusBefore) {
+            auditService.logAfterCommit(AuditKind.STATUS_CHANGED, actorId, saved.getId(),
+                    Map.of("oldStatus", statusBefore.name(), "newStatus", saved.getStatus().name()));
+        } else {
+            auditService.logAfterCommit(AuditKind.METADATA_UPDATED, actorId, saved.getId(), null);
+        }
+
+        if (fileReplaced) {
+            thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
+        }
+
         return saved;
     }
 
     public Document updateDocumentTags(UUID docId, List<String> tagNames) {
         Document doc = documentRepository.findById(docId)
                 .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + docId));
+        doc.setTags(resolveTags(tagNames));
+        return documentRepository.save(doc);
+    }
 
-        Set<Tag> newTags = new HashSet<>();
-
+    /**
+     * Resolves a list of tag-name strings to {@link Tag} entities, trimming
+     * whitespace and skipping blank entries. Single source of truth for
+     * "name string → Tag" so the find-or-create policy stays consistent
+     * across single-doc updates ({@link #updateDocumentTags}), bulk edits
+     * ({@link #applyBulkEditToDocument}), and the upload-batch path
+     * ({@code applyBatchMetadata}).
+     */
+    private Set<Tag> resolveTags(List<String> tagNames) {
+        if (tagNames == null || tagNames.isEmpty()) return new HashSet<>();
+        Set<Tag> resolved = new HashSet<>();
         for (String name : tagNames) {
-            // Clean the string
             String cleanName = name.trim();
-            if (cleanName.isEmpty())
-                continue;
+            if (cleanName.isEmpty()) continue;
+            resolved.add(tagService.findOrCreate(cleanName));
+        }
+        return resolved;
+    }
 
-            newTags.add(tagService.findOrCreate(cleanName));
+    /**
+     * Returns all document IDs matching the given filter parameters, ignoring
+     * pagination. Used by the bulk-edit "Alle X editieren" fast path so the
+     * frontend can replace the selection with every match across pages in one
+     * round-trip.
+     */
+    @Transactional(readOnly = true)
+    public List<UUID> findIdsForFilter(String text, LocalDate from, LocalDate to, UUID sender, UUID receiver,
+                                       List<String> tags, String tagQ, DocumentStatus status, TagOperator tagOperator) {
+        boolean hasText = StringUtils.hasText(text);
+        List<UUID> rankedIds = null;
+        if (hasText) {
+            rankedIds = documentRepository.findRankedIdsByFts(text);
+            if (rankedIds.isEmpty()) return List.of();
         }
 
-        doc.setTags(newTags);
-        return documentRepository.save(doc);
+        Specification<Document> spec = buildSearchSpec(
+                hasText, rankedIds, from, to, sender, receiver, tags, tagQ, status, tagOperator);
+        return documentRepository.findAll(spec).stream().map(Document::getId).toList();
+    }
+
+    /**
+     * Single source of truth for the search Specification chain. Shared by
+     * {@link #searchDocuments} (paged + sorted) and {@link #findIdsForFilter}
+     * (uncapped, ID-only). Caller does its own FTS short-circuit when the
+     * full-text query returned no rows.
+     */
+    private Specification<Document> buildSearchSpec(boolean hasText, List<UUID> ftsIds,
+                                                    LocalDate from, LocalDate to,
+                                                    UUID sender, UUID receiver,
+                                                    List<String> tags, String tagQ,
+                                                    DocumentStatus status, TagOperator tagOperator) {
+        boolean useOrLogic = tagOperator == TagOperator.OR;
+        List<Set<UUID>> expandedTagSets = tagService.expandTagNamesToDescendantIdSets(tags);
+        Specification<Document> textSpec = hasText ? hasIds(ftsIds) : (root, query, cb) -> null;
+        return Specification.where(textSpec)
+                .and(isBetween(from, to))
+                .and(hasSender(sender))
+                .and(hasReceiver(receiver))
+                .and(hasTags(expandedTagSets, useOrLogic))
+                .and(hasTagPartial(tagQ))
+                .and(hasStatus(status));
+    }
+
+    /**
+     * Returns lightweight summaries (id, title, server PDF URL) for the given
+     * document IDs. Unknown IDs are silently dropped — the consumer is the
+     * bulk-edit page's left strip, where missing previews would already be
+     * obvious; surfacing them as errors here adds no value.
+     */
+    @Transactional(readOnly = true)
+    public List<DocumentBatchSummary> batchMetadata(List<UUID> ids) {
+        if (ids == null || ids.isEmpty()) return List.of();
+        return documentRepository.findAllById(ids).stream()
+                .map(d -> new DocumentBatchSummary(
+                        d.getId(),
+                        d.getTitle() != null ? d.getTitle() : d.getOriginalFilename(),
+                        "/api/documents/" + d.getId() + "/file"))
+                .toList();
+    }
+
+    /**
+     * Applies a bulk-edit DTO to a single document atomically.
+     * Tags and receivers are additive (merged into existing sets); sender and the
+     * three location fields are replace-on-non-blank (null/blank means "no change").
+     * Wrapped in its own transaction so a failure on one document never partially
+     * mutates another in the controller's batch loop.
+     *
+     * Each successful update emits a {@link AuditKind#METADATA_UPDATED} audit
+     * event tagged {@code source=BULK_EDIT} and writes a row to
+     * {@code document_versions} so the family archive's "who changed what"
+     * trail stays complete across both single- and bulk-doc edit paths.
+     *
+     * NOTE on N+1: tag and person resolution happens per-document. With 500
+     * documents × 10 tags this fans out to ~5000 tag-resolve queries per
+     * request. Acceptable today because the family archive is bounded at
+     * ~1500 documents total. Tracked as a perf follow-up.
+     */
+    @Transactional
+    public Document applyBulkEditToDocument(UUID id, DocumentBulkEditDTO dto, UUID actorId) {
+        Document doc = documentRepository.findById(id)
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + id));
+
+        if (dto.getTagNames() != null && !dto.getTagNames().isEmpty()) {
+            Set<Tag> merged = new HashSet<>(doc.getTags());
+            merged.addAll(resolveTags(dto.getTagNames()));
+            doc.setTags(merged);
+        }
+
+        if (dto.getSenderId() != null) {
+            doc.setSender(personService.getById(dto.getSenderId()));
+        }
+
+        if (dto.getReceiverIds() != null && !dto.getReceiverIds().isEmpty()) {
+            Set<Person> merged = new HashSet<>(doc.getReceivers());
+            merged.addAll(personService.getAllById(dto.getReceiverIds()));
+            doc.setReceivers(merged);
+        }
+
+        if (StringUtils.hasText(dto.getDocumentLocation())) {
+            doc.setDocumentLocation(dto.getDocumentLocation());
+        }
+        if (StringUtils.hasText(dto.getArchiveBox())) {
+            doc.setArchiveBox(dto.getArchiveBox());
+        }
+        if (StringUtils.hasText(dto.getArchiveFolder())) {
+            doc.setArchiveFolder(dto.getArchiveFolder());
+        }
+
+        Document saved = documentRepository.save(doc);
+        documentVersionService.recordVersion(saved);
+        auditService.logAfterCommit(AuditKind.METADATA_UPDATED, actorId, saved.getId(),
+                Map.of("source", "BULK_EDIT"));
+        return saved;
     }
 
     /**
@@ -282,6 +494,33 @@ public class DocumentService {
         return documentRepository.save(doc);
     }
 
+    @Transactional
+    public Document attachFile(UUID id, MultipartFile file, UUID actorId) {
+        Document doc = documentRepository.findById(id)
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + id));
+        FileService.UploadResult upload;
+        try {
+            upload = fileService.uploadFile(file, file.getOriginalFilename());
+        } catch (IOException e) {
+            throw DomainException.internal(ErrorCode.FILE_UPLOAD_FAILED, "Failed to upload file: " + e.getMessage());
+        }
+        doc.setFilePath(upload.s3Key());
+        doc.setFileHash(upload.fileHash());
+        doc.setOriginalFilename(file.getOriginalFilename());
+        doc.setContentType(file.getContentType());
+        boolean wasPlaceholder = doc.getStatus() == DocumentStatus.PLACEHOLDER;
+        if (wasPlaceholder) {
+            doc.setStatus(DocumentStatus.UPLOADED);
+        }
+        Document saved = documentRepository.save(doc);
+        documentVersionService.recordVersion(saved);
+        thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
+        if (wasPlaceholder) {
+            auditService.logAfterCommit(AuditKind.FILE_UPLOADED, actorId, saved.getId(), null);
+        }
+        return saved;
+    }
+
     // 0. Zuletzt aktive Dokumente (sortiert nach updatedAt DESC)
     public List<Document> getRecentActivity(int size) {
         return documentRepository.findAll(
@@ -290,33 +529,30 @@ public class DocumentService {
     }
 
     // 1. Allgemeine Suche (für das Suchfeld im Frontend)
-    public List<Document> searchDocuments(String text, LocalDate from, LocalDate to, UUID sender, UUID receiver, List<String> tags, String tagQ, DocumentStatus status, DocumentSort sort, String dir) {
+    public DocumentSearchResult searchDocuments(String text, LocalDate from, LocalDate to, UUID sender, UUID receiver, List<String> tags, String tagQ, DocumentStatus status, DocumentSort sort, String dir, TagOperator tagOperator, Pageable pageable) {
         boolean hasText = StringUtils.hasText(text);
         List<UUID> rankedIds = null;
 
         if (hasText) {
             rankedIds = documentRepository.findRankedIdsByFts(text);
-            if (rankedIds.isEmpty()) return List.of();
+            if (rankedIds.isEmpty()) return DocumentSearchResult.of(List.of());
         }
 
-        Specification<Document> textSpec = hasText ? hasIds(rankedIds) : (root, query, cb) -> null;
-        Specification<Document> spec = Specification.where(textSpec)
-                .and(isBetween(from, to))
-                .and(hasSender(sender))
-                .and(hasReceiver(receiver))
-                .and(hasTags(tags))
-                .and(hasTagPartial(tagQ))
-                .and(hasStatus(status));
+        Specification<Document> spec = buildSearchSpec(
+                hasText, rankedIds, from, to, sender, receiver, tags, tagQ, status, tagOperator);
 
-        // SENDER and RECEIVER are sorted in-memory because JPA's Sort.by("sender.lastName")
-        // generates an INNER JOIN that silently drops documents with null sender/receivers.
+        // SENDER, RECEIVER and RELEVANCE sorts load the full match set and slice in memory.
+        // JPA's Sort.by("sender.lastName") generates an INNER JOIN that silently drops
+        // documents with null sender/receivers; RELEVANCE maps a DB order to an external
+        // rank list. Cost scales linearly with match count — acceptable while documents
+        // stays under ~10k rows. Past that, replace with SQL-level LEFT JOIN sort.
         if (sort == DocumentSort.RECEIVER) {
-            List<Document> results = documentRepository.findAll(spec);
-            return sortByFirstReceiver(results, dir);
+            List<Document> sorted = sortByFirstReceiver(documentRepository.findAll(spec), dir);
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
         if (sort == DocumentSort.SENDER) {
-            List<Document> results = documentRepository.findAll(spec);
-            return sortBySender(results, dir);
+            List<Document> sorted = sortBySender(documentRepository.findAll(spec), dir);
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
 
         // RELEVANCE: default when text present and no explicit sort given
@@ -325,14 +561,47 @@ public class DocumentService {
             List<Document> results = documentRepository.findAll(spec);
             Map<UUID, Integer> rankMap = new HashMap<>();
             for (int i = 0; i < rankedIds.size(); i++) rankMap.put(rankedIds.get(i), i);
-            return results.stream()
+            List<Document> sorted = results.stream()
                     .sorted(Comparator.comparingInt(
                             doc -> rankMap.getOrDefault(doc.getId(), Integer.MAX_VALUE)))
                     .toList();
+            return buildResultPaged(pageSlice(sorted, pageable), text, pageable, sorted.size());
         }
 
-        Sort springSort = resolveSort(sort, dir);
-        return documentRepository.findAll(spec, springSort);
+        // Fast path — push sort + paging into the DB and enrich only the returned slice.
+        PageRequest pageRequest = PageRequest.of(pageable.getPageNumber(), pageable.getPageSize(), resolveSort(sort, dir));
+        Page<Document> page = documentRepository.findAll(spec, pageRequest);
+        return buildResultPaged(page.getContent(), text, pageable, page.getTotalElements());
+    }
+
+    private static <T> List<T> pageSlice(List<T> sorted, Pageable pageable) {
+        int from = Math.min((int) pageable.getOffset(), sorted.size());
+        int to = Math.min(from + pageable.getPageSize(), sorted.size());
+        return sorted.subList(from, to);
+    }
+
+    private DocumentSearchResult buildResultPaged(List<Document> slice, String text, Pageable pageable, long totalElements) {
+        return DocumentSearchResult.paged(enrichItems(slice, text), pageable, totalElements);
+    }
+
+    private List<DocumentSearchItem> enrichItems(List<Document> documents, String text) {
+        List<Document> colorResolved = resolveDocumentTagColors(documents);
+        Map<UUID, SearchMatchData> matchData = enrichWithMatchData(colorResolved, text);
+
+        List<UUID> docIds = colorResolved.stream().map(Document::getId).toList();
+        Map<UUID, Integer> completionByDoc = fetchCompletionPercentages(docIds);
+        Map<UUID, List<ActivityActorDTO>> contributorsByDoc = auditLogQueryService.findRecentContributorsPerDocument(docIds);
+
+        return colorResolved.stream().map(doc -> new DocumentSearchItem(
+                doc,
+                matchData.getOrDefault(doc.getId(), SearchMatchData.empty()),
+                completionByDoc.getOrDefault(doc.getId(), 0),
+                contributorsByDoc.getOrDefault(doc.getId(), List.of())
+        )).toList();
+    }
+
+    private Map<UUID, Integer> fetchCompletionPercentages(List<UUID> docIds) {
+        return transcriptionBlockQueryService.getCompletionStats(docIds);
     }
 
     private Sort resolveSort(DocumentSort sort, String dir) {
@@ -423,8 +692,14 @@ public class DocumentService {
     }
 
     public Document getDocumentById(UUID id) {
-        return documentRepository.findById(id)
+        Document doc = documentRepository.findById(id)
                 .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + id));
+        tagService.resolveEffectiveColors(doc.getTags());
+        return doc;
+    }
+
+    public List<Document> getDocumentsByIds(List<UUID> ids) {
+        return documentRepository.findAllById(ids);
     }
 
     public List<Document> getDocumentsWithoutVersions() {
@@ -456,7 +731,7 @@ public class DocumentService {
         PageRequest pageable = PageRequest.of(0, size, Sort.by(Sort.Direction.DESC, "createdAt"));
         return documentRepository.findByMetadataCompleteFalse(pageable)
                 .stream()
-                .map(doc -> new IncompleteDocumentDTO(doc.getId(), doc.getTitle()))
+                .map(doc -> new IncompleteDocumentDTO(doc.getId(), doc.getTitle(), doc.getCreatedAt()))
                 .toList();
     }
 
@@ -503,6 +778,12 @@ public class DocumentService {
 
     // ─── private helpers ──────────────────────────────────────────────────────
 
+    private List<Document> resolveDocumentTagColors(List<Document> docs) {
+        List<Tag> allTags = docs.stream().flatMap(d -> d.getTags().stream()).toList();
+        tagService.resolveEffectiveColors(allTags);
+        return docs;
+    }
+
     private static String stripExtension(String filename) {
         if (filename == null) return null;
         int dot = filename.lastIndexOf('.');
@@ -584,6 +865,93 @@ public class DocumentService {
         return null;
     }
 
+    /**
+     * Calls {@code findEnrichmentData} and converts the raw Object[] rows into a
+     * {@link SearchMatchData} per document. Short-circuits when the list is empty or
+     * the query is blank (no text search active).
+     */
+    private Map<UUID, SearchMatchData> enrichWithMatchData(List<Document> docs, String query) {
+        if (docs.isEmpty() || !StringUtils.hasText(query)) return Map.of();
+        List<UUID> ids = docs.stream().map(Document::getId).toList();
+        Map<UUID, SearchMatchData> result = new HashMap<>();
+        for (Object[] row : documentRepository.findEnrichmentData(ids, query)) {
+            UUID docId = (UUID) row[0];
+            String titleHeadline = (String) row[1];
+            String snippetHeadline = (String) row[2];
+            Boolean senderMatched = (Boolean) row[3];
+            String receiverIdsStr = (String) row[4];
+            String tagIdsStr = (String) row[5];
+            String summaryHeadline = (String) row[6];
+            ParsedHighlight snippet = parseHighlight(snippetHeadline);
+            ParsedHighlight summary = parseHighlight(summaryHeadline);
+            result.put(docId, new SearchMatchData(
+                    snippet != null ? snippet.cleanText() : null,
+                    parseTitleOffsets(titleHeadline),
+                    senderMatched != null && senderMatched,
+                    parseUUIDs(receiverIdsStr),
+                    parseUUIDs(tagIdsStr),
+                    snippet != null ? snippet.offsets() : List.of(),
+                    summary != null ? summary.cleanText() : null,
+                    summary != null ? summary.offsets() : List.of()
+            ));
+        }
+        return result;
+    }
+
+    /** Clean text + highlight offsets parsed from a {@code ts_headline} sentinel-delimited string. */
+    public record ParsedHighlight(String cleanText, List<MatchOffset> offsets) {}
+
+    /**
+     * Parses a {@code ts_headline} result that uses {@code chr(1)}/{@code chr(2)} as
+     * start/stop delimiters. Returns the clean text (delimiters stripped) together with
+     * the character offsets of each highlighted span. Returns {@code null} when
+     * {@code headline} is {@code null}.
+     */
+    public static ParsedHighlight parseHighlight(String headline) {
+        if (headline == null) return null;
+        StringBuilder clean = new StringBuilder(headline.length());
+        List<MatchOffset> offsets = new ArrayList<>();
+        int i = 0;
+        int pos = 0; // position in the clean string (no delimiters)
+        while (i < headline.length()) {
+            char c = headline.charAt(i);
+            if (c == '\u0001') {
+                int start = pos;
+                i++;
+                while (i < headline.length() && headline.charAt(i) != '\u0002') {
+                    clean.append(headline.charAt(i));
+                    i++;
+                    pos++;
+                }
+                offsets.add(new MatchOffset(start, pos - start));
+                i++; // skip \u0002
+            } else {
+                clean.append(c);
+                i++;
+                pos++;
+            }
+        }
+        return new ParsedHighlight(clean.toString(), offsets);
+    }
+
+    /**
+     * Extracts only the {@link MatchOffset} list from a title headline.
+     * The clean title text comes from the {@link Document} entity itself.
+     */
+    private static List<MatchOffset> parseTitleOffsets(String headline) {
+        ParsedHighlight parsed = parseHighlight(headline);
+        return parsed != null ? parsed.offsets() : List.of();
+    }
+
+    private static List<UUID> parseUUIDs(String csv) {
+        if (csv == null || csv.isBlank()) return List.of();
+        return Arrays.stream(csv.split(","))
+                .map(String::trim)
+                .filter(s -> !s.isEmpty())
+                .map(UUID::fromString)
+                .toList();
+    }
+
     private static String sha256Hex(byte[] bytes) {
         try {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
@@ -597,4 +965,5 @@ public class DocumentService {
             throw new IllegalStateException("SHA-256 not available", e);
         }
     }
+
 }

backend/src/main/java/org/raddatz/familienarchiv/service/DocumentVersionService.java

@@ -100,7 +100,7 @@ public class DocumentVersionService {
             return null;
         }
         try {
-            return userService.findByUsername(auth.getName());
+            return userService.findByEmail(auth.getName());
         } catch (Exception e) {
             log.warn("Could not resolve editor for version snapshot: {}", e.getMessage());
             return null;
@@ -114,7 +114,7 @@ public class DocumentVersionService {
         if (first != null && !first.isBlank() && last != null && !last.isBlank()) {
             return first + " " + last;
         }
-        return user.getUsername();
+        return user.getEmail();
     }
 
     private String serializeSnapshot(Document doc) {

backend/src/main/java/org/raddatz/familienarchiv/service/FileService.java

@@ -112,6 +112,27 @@ public class FileService {
         }
     }
 
+    /**
+     * Opens a streaming download from S3/MinIO. The caller is responsible for
+     * closing the returned stream — typically via try-with-resources. Preferred
+     * over {@link #downloadFileBytes(String)} for large files (multi-MB PDFs
+     * during thumbnail generation) because it avoids loading the entire file
+     * into heap memory.
+     */
+    public InputStream downloadFileStream(String s3Key) throws IOException {
+        try {
+            GetObjectRequest getObjectRequest = GetObjectRequest.builder()
+                    .bucket(bucketName)
+                    .key(s3Key)
+                    .build();
+            return s3Client.getObject(getObjectRequest);
+        } catch (NoSuchKeyException e) {
+            throw new StorageFileNotFoundException("File not found in storage: " + s3Key);
+        } catch (S3Exception e) {
+            throw new IOException("Failed to open stream from storage: " + e.getMessage(), e);
+        }
+    }
+
     /**
      * Generates a presigned URL for downloading an object from S3/MinIO.
      * Valid for 1 hour — covers multi-page documents on CPU-only OCR hardware

backend/src/main/java/org/raddatz/familienarchiv/service/InviteService.java

@@ -0,0 +1,165 @@
+package org.raddatz.familienarchiv.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.dto.CreateInviteRequest;
+import org.raddatz.familienarchiv.dto.InviteListItemDTO;
+import org.raddatz.familienarchiv.dto.RegisterRequest;
+import org.raddatz.familienarchiv.exception.DomainException;
+import org.raddatz.familienarchiv.exception.ErrorCode;
+import org.raddatz.familienarchiv.model.AppUser;
+import org.raddatz.familienarchiv.model.InviteToken;
+import org.raddatz.familienarchiv.model.UserGroup;
+import org.raddatz.familienarchiv.repository.InviteTokenRepository;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.security.SecureRandom;
+import java.util.*;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class InviteService {
+
+    static final int MIN_PASSWORD_LENGTH = 8;
+    private static final String CODE_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+    private static final int CODE_LENGTH = 10;
+    private static final int MAX_CODE_ATTEMPTS = 10;
+    private static final SecureRandom SECURE_RANDOM = new SecureRandom();
+
+    private final InviteTokenRepository inviteTokenRepository;
+    private final UserService userService;
+
+    public String generateCode() {
+        for (int attempt = 0; attempt < MAX_CODE_ATTEMPTS; attempt++) {
+            String code = buildRandomCode();
+            if (inviteTokenRepository.findByCode(code).isEmpty()) {
+                return code;
+            }
+        }
+        throw DomainException.internal(ErrorCode.INTERNAL_ERROR, "Failed to generate unique invite code after " + MAX_CODE_ATTEMPTS + " attempts");
+    }
+
+    public InviteToken validateCode(String code) {
+        InviteToken token = inviteTokenRepository.findByCode(code)
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.INVITE_NOT_FOUND, "Invite not found: " + code));
+        checkTokenState(token);
+        return token;
+    }
+
+    @Transactional
+    public InviteToken createInvite(CreateInviteRequest dto, AppUser creator) {
+        Set<UUID> groupIds = new HashSet<>();
+        if (dto.getGroupIds() != null && !dto.getGroupIds().isEmpty()) {
+            List<UserGroup> groups = userService.findGroupsByIds(dto.getGroupIds());
+            groups.forEach(g -> groupIds.add(g.getId()));
+        }
+
+        InviteToken token = InviteToken.builder()
+                .code(generateCode())
+                .label(dto.getLabel())
+                .maxUses(dto.getMaxUses())
+                .prefillFirstName(dto.getPrefillFirstName())
+                .prefillLastName(dto.getPrefillLastName())
+                .prefillEmail(dto.getPrefillEmail())
+                .groupIds(groupIds)
+                .expiresAt(dto.getExpiresAt())
+                .createdBy(creator)
+                .build();
+
+        return inviteTokenRepository.save(token);
+    }
+
+    @Transactional
+    public AppUser redeemInvite(RegisterRequest dto) {
+        InviteToken token = inviteTokenRepository.findByCodeForUpdate(dto.getCode())
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.INVITE_NOT_FOUND, "Invite not found: " + dto.getCode()));
+
+        checkTokenState(token);
+
+        if (dto.getPassword() == null || dto.getPassword().length() < MIN_PASSWORD_LENGTH) {
+            throw DomainException.badRequest(ErrorCode.VALIDATION_ERROR,
+                    "Password must be at least " + MIN_PASSWORD_LENGTH + " characters");
+        }
+
+        AppUser user = userService.createUser(
+                dto.getEmail(),
+                dto.getPassword(),
+                dto.getFirstName(),
+                dto.getLastName(),
+                token.getGroupIds()
+        );
+
+        userService.updateNotificationPreferences(user.getId(), dto.isNotifyOnMention(), dto.isNotifyOnMention());
+
+        token.setUseCount(token.getUseCount() + 1);
+        inviteTokenRepository.save(token);
+
+        log.info("User {} registered via invite code {}", dto.getEmail(), dto.getCode());
+        return user;
+    }
+
+    @Transactional
+    public void revokeInvite(UUID id) {
+        InviteToken token = inviteTokenRepository.findById(id)
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.INVITE_NOT_FOUND, "Invite not found: " + id));
+        token.setRevoked(true);
+        inviteTokenRepository.save(token);
+    }
+
+    public List<InviteListItemDTO> listInvites(boolean activeOnly, String appBaseUrl) {
+        List<InviteToken> tokens = activeOnly
+                ? inviteTokenRepository.findActive()
+                : inviteTokenRepository.findAllOrderedByCreatedAt();
+        return tokens.stream().map(t -> toListItemDTO(t, appBaseUrl)).toList();
+    }
+
+    public InviteListItemDTO toListItemDTO(InviteToken token, String appBaseUrl) {
+        String status;
+        if (token.isRevoked()) status = "revoked";
+        else if (token.isExpired()) status = "expired";
+        else if (token.isExhausted()) status = "exhausted";
+        else status = "active";
+
+        return InviteListItemDTO.builder()
+                .id(token.getId())
+                .code(token.getCode())
+                .displayCode(formatDisplayCode(token.getCode()))
+                .label(token.getLabel())
+                .useCount(token.getUseCount())
+                .maxUses(token.getMaxUses())
+                .expiresAt(token.getExpiresAt())
+                .revoked(token.isRevoked())
+                .status(status)
+                .createdAt(token.getCreatedAt())
+                .shareableUrl(appBaseUrl + "/register?code=" + token.getCode())
+                .build();
+    }
+
+    private void checkTokenState(InviteToken token) {
+        if (token.isRevoked()) {
+            throw DomainException.conflict(ErrorCode.INVITE_REVOKED, "Invite has been revoked");
+        }
+        if (token.isExpired()) {
+            throw new DomainException(ErrorCode.INVITE_EXPIRED, org.springframework.http.HttpStatus.GONE,
+                    "Invite has expired");
+        }
+        if (token.isExhausted()) {
+            throw DomainException.conflict(ErrorCode.INVITE_EXHAUSTED, "Invite use limit reached");
+        }
+    }
+
+    private String buildRandomCode() {
+        StringBuilder sb = new StringBuilder(CODE_LENGTH);
+        for (int i = 0; i < CODE_LENGTH; i++) {
+            sb.append(CODE_ALPHABET.charAt(SECURE_RANDOM.nextInt(CODE_ALPHABET.length())));
+        }
+        return sb.toString();
+    }
+
+    public static String formatDisplayCode(String code) {
+        if (code == null || code.length() != CODE_LENGTH) return code;
+        return code.substring(0, 5) + "-" + code.substring(5);
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/service/MassImportService.java

@@ -59,6 +59,7 @@ public class MassImportService {
     private final PersonService personService;
     private final TagService tagService;
     private final S3Client s3Client;
+    private final ThumbnailAsyncRunner thumbnailAsyncRunner;
 
     @Value("${app.s3.bucket}")
     private String bucketName;
@@ -332,7 +333,10 @@ public class MassImportService {
         if (tag != null) doc.getTags().add(tag);
         doc.setMetadataComplete(metadataComplete);
 
-        documentRepository.save(doc);
+        Document saved = documentRepository.save(doc);
+        if (file.isPresent()) {
+            thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
+        }
         log.info("Importiert{}: {}", file.isEmpty() ? " (nur Metadaten)" : "", originalFilename);
     }
 

backend/src/main/java/org/raddatz/familienarchiv/service/OcrAsyncRunner.java

@@ -9,10 +9,12 @@ import org.raddatz.familienarchiv.repository.OcrJobRepository;
 import org.springframework.scheduling.annotation.Async;
 import org.springframework.stereotype.Component;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 
 @Component
 @RequiredArgsConstructor
@@ -29,6 +31,7 @@ public class OcrAsyncRunner {
     private final OcrJobRepository ocrJobRepository;
     private final OcrJobDocumentRepository ocrJobDocumentRepository;
     private final OcrProgressService ocrProgressService;
+    private final SenderModelService senderModelService;
 
     @Async
     public void runSingleDocument(UUID jobId, UUID documentId, UUID userId) {
@@ -68,12 +71,18 @@ public class OcrAsyncRunner {
 
             String pdfUrl = fileService.generatePresignedUrl(doc.getFilePath());
 
+            String senderModelPath = null;
+            if (doc.getSender() != null && doc.getScriptType() == ScriptType.HANDWRITING_KURRENT) {
+                senderModelPath = senderModelService.maybeGetModelPath(doc.getSender().getId()).orElse(null);
+            }
+
             AtomicInteger blockCounter = new AtomicInteger(0);
             AtomicInteger currentPage = new AtomicInteger(0);
             AtomicInteger skippedPages = new AtomicInteger(0);
             AtomicInteger totalPages = new AtomicInteger(0);
 
-            ocrClient.streamBlocks(pdfUrl, doc.getScriptType(), regions, event -> {
+            final String finalSenderModelPath = senderModelPath;
+            ocrClient.streamBlocks(pdfUrl, doc.getScriptType(), regions, finalSenderModelPath, event -> {
                 switch (event) {
                     case OcrStreamEvent.Start start -> {
                         totalPages.set(start.totalPages());
@@ -82,6 +91,10 @@ public class OcrAsyncRunner {
                             ocrJobDocumentRepository.save(jobDoc);
                         }
                     }
+                    case OcrStreamEvent.Preprocessing preprocessing -> {
+                        updateProgress(job, "PREPROCESSING_PAGE:" + preprocessing.pageNumber()
+                                + ":" + totalPages.get());
+                    }
                     case OcrStreamEvent.Page page -> {
                         for (OcrBlockResult block : page.blocks()) {
                             createSingleBlock(documentId, block, userId,
@@ -203,7 +216,25 @@ public class OcrAsyncRunner {
         clearExistingBlocks(documentId);
 
         String pdfUrl = fileService.generatePresignedUrl(doc.getFilePath());
-        List<OcrBlockResult> blocks = ocrClient.extractBlocks(pdfUrl, doc.getScriptType());
+
+        String senderModelPath = null;
+        if (doc.getSender() != null && doc.getScriptType() == ScriptType.HANDWRITING_KURRENT) {
+            senderModelPath = senderModelService.maybeGetModelPath(doc.getSender().getId()).orElse(null);
+        }
+
+        final AtomicReference<List<OcrBlockResult>> blocksRef = new AtomicReference<>();
+        final String finalSenderModelPath = senderModelPath;
+        ocrClient.streamBlocks(pdfUrl, doc.getScriptType(), null, finalSenderModelPath, event -> {
+            switch (event) {
+                case OcrStreamEvent.Page page -> {
+                    blocksRef.compareAndSet(null, new ArrayList<>());
+                    blocksRef.get().addAll(page.blocks());
+                }
+                default -> {}
+            }
+        });
+
+        List<OcrBlockResult> blocks = blocksRef.get() != null ? blocksRef.get() : List.of();
         createTranscriptionBlocks(documentId, blocks, userId, doc.getFileHash());
     }
 

backend/src/main/java/org/raddatz/familienarchiv/service/OcrClient.java

@@ -1,6 +1,7 @@
 package org.raddatz.familienarchiv.service;
 
 import org.raddatz.familienarchiv.model.ScriptType;
+import org.springframework.lang.Nullable;
 
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
@@ -37,15 +38,27 @@ public interface OcrClient {
     TrainingResult segtrainModel(byte[] trainingDataZip);
 
     /**
-     * Stream OCR results page-by-page via NDJSON. Implementations should override
-     * this method. The default exists only for backward compatibility during migration
-     * — it calls extractBlocks() and synthesizes events from the collected result.
+     * Fine-tune the Kurrent model for a specific sender.
      *
-     * @param regions optional list of pre-drawn annotation regions; when non-null,
-     *                the OCR service runs in guided mode (crop + recognize per region)
+     * @param trainingDataZip raw ZIP bytes produced by TrainingDataExportService.exportForSender()
+     * @param outputModelPath where to save the trained model (e.g. /app/models/sender_{uuid}.mlmodel)
+     * @return training result metrics
+     */
+    TrainingResult trainSenderModel(byte[] trainingDataZip, String outputModelPath);
+
+    /**
+     * Stream OCR results page-by-page via NDJSON, optionally using a sender-specific model.
+     * The default implementation synthesizes events from extractBlocks() for backward compatibility.
+     * Implementations that support real streaming (e.g. RestClientOcrClient) override this.
+     *
+     * @param regions         optional list of pre-drawn annotation regions; when non-null,
+     *                        the OCR service runs in guided mode (crop + recognize per region)
+     * @param senderModelPath optional path to a per-sender model file; null means use base model
      */
     default void streamBlocks(String pdfUrl, ScriptType scriptType,
-                               List<OcrRegion> regions, Consumer<OcrStreamEvent> handler) {
+                               List<OcrRegion> regions,
+                               @Nullable String senderModelPath,
+                               Consumer<OcrStreamEvent> handler) {
         List<OcrBlockResult> allBlocks = extractBlocks(pdfUrl, scriptType);
 
         LinkedHashMap<Integer, List<OcrBlockResult>> byPage = new LinkedHashMap<>();
@@ -62,4 +75,9 @@ public interface OcrClient {
 
         handler.accept(new OcrStreamEvent.Done(allBlocks.size(), 0));
     }
+
+    default void streamBlocks(String pdfUrl, ScriptType scriptType,
+                               List<OcrRegion> regions, Consumer<OcrStreamEvent> handler) {
+        streamBlocks(pdfUrl, scriptType, regions, null, handler);
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/service/OcrStreamEvent.java

@@ -6,6 +6,8 @@ public sealed interface OcrStreamEvent {
 
     record Start(int totalPages) implements OcrStreamEvent {}
 
+    record Preprocessing(int pageNumber) implements OcrStreamEvent {}
+
     record Page(int pageNumber, List<OcrBlockResult> blocks) implements OcrStreamEvent {}
 
     record Error(int pageNumber, String message) implements OcrStreamEvent {}

backend/src/main/java/org/raddatz/familienarchiv/service/OcrTrainingService.java

@@ -2,9 +2,12 @@ package org.raddatz.familienarchiv.service;
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.dto.TrainingHistoryResponse;
+import org.raddatz.familienarchiv.dto.TrainingInfoResponse;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
 import org.raddatz.familienarchiv.model.OcrTrainingRun;
+import org.raddatz.familienarchiv.model.SenderModel;
 import org.raddatz.familienarchiv.model.TrainingStatus;
 import org.raddatz.familienarchiv.repository.OcrTrainingRunRepository;
 import org.raddatz.familienarchiv.repository.TranscriptionBlockRepository;
@@ -17,9 +20,11 @@ import org.springframework.transaction.support.TransactionTemplate;
 
 import java.io.ByteArrayOutputStream;
 import java.time.Instant;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.UUID;
 
 @Service
@@ -34,16 +39,8 @@ public class OcrTrainingService {
     private final OcrHealthClient ocrHealthClient;
     private final TranscriptionBlockRepository blockRepository;
     private final TransactionTemplate txTemplate;
-
-    public record TrainingInfoResponse(
-            int availableBlocks,
-            int totalOcrBlocks,
-            int availableDocuments,
-            int availableSegBlocks,
-            boolean ocrServiceAvailable,
-            OcrTrainingRun lastRun,
-            List<OcrTrainingRun> runs
-    ) {}
+    private final PersonService personService;
+    private final SenderModelService senderModelService;
 
     private void assertNoRunningTraining() {
         if (trainingRunRepository.findFirstByStatus(TrainingStatus.RUNNING).isPresent()) {
@@ -195,9 +192,21 @@ public class OcrTrainingService {
         int totalOcrBlocks = (int) blockRepository.count();
         int availableSegBlocks = segmentationTrainingExportService.querySegmentationBlocks().size();
 
-        List<OcrTrainingRun> recentRuns = trainingRunRepository.findTop10ByOrderByCreatedAtDesc();
+        List<OcrTrainingRun> recentRuns = trainingRunRepository.findTop20ByOrderByCreatedAtDesc();
         OcrTrainingRun lastRun = recentRuns.isEmpty() ? null : recentRuns.get(0);
 
+        List<SenderModel> senderModels = senderModelService.getAllSenderModels();
+
+        List<UUID> allPersonIds = senderModels.stream()
+                .map(SenderModel::getPersonId)
+                .distinct()
+                .toList();
+        Map<String, String> personNames = new HashMap<>();
+        if (!allPersonIds.isEmpty()) {
+            personService.getAllById(allPersonIds)
+                    .forEach(p -> personNames.put(p.getId().toString(), p.getDisplayName()));
+        }
+
         return new TrainingInfoResponse(
                 eligibleBlocks.size(),
                 totalOcrBlocks,
@@ -205,10 +214,23 @@ public class OcrTrainingService {
                 availableSegBlocks,
                 ocrHealthClient.isHealthy(),
                 lastRun,
-                recentRuns
+                recentRuns,
+                personNames,
+                senderModels
         );
     }
 
+    public TrainingHistoryResponse getGlobalTrainingHistory() {
+        List<OcrTrainingRun> runs = trainingRunRepository.findByPersonIdIsNullOrderByCreatedAtDesc();
+        return new TrainingHistoryResponse(runs, Map.of());
+    }
+
+    public TrainingHistoryResponse getSenderTrainingHistory(UUID personId) {
+        String personName = personService.getById(personId).getDisplayName();
+        List<OcrTrainingRun> runs = trainingRunRepository.findByPersonIdOrderByCreatedAtDesc(personId);
+        return new TrainingHistoryResponse(runs, Map.of(personId.toString(), personName));
+    }
+
     @EventListener(ApplicationReadyEvent.class)
     @Transactional
     public void recoverOrphanedRuns() {
@@ -224,15 +246,4 @@ public class OcrTrainingService {
         });
     }
 
-    public Map<String, Object> buildTrainingInfoMap(TrainingInfoResponse info) {
-        return Map.of(
-                "availableBlocks", info.availableBlocks(),
-                "totalOcrBlocks", info.totalOcrBlocks(),
-                "availableDocuments", info.availableDocuments(),
-                "availableSegBlocks", info.availableSegBlocks(),
-                "ocrServiceAvailable", info.ocrServiceAvailable(),
-                "lastRun", info.lastRun() != null ? info.lastRun() : Map.of(),
-                "runs", info.runs()
-        );
-    }
 }

backend/src/main/java/org/raddatz/familienarchiv/service/RestClientOcrClient.java

@@ -14,6 +14,7 @@ import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.JdkClientHttpRequestFactory;
+import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Component;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -102,6 +103,13 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
                 .toList();
     }
 
+    private RestClient.RequestBodySpec addTrainingAuth(RestClient.RequestBodySpec spec) {
+        if (trainingToken != null && !trainingToken.isBlank()) {
+            return spec.header("X-Training-Token", trainingToken);
+        }
+        return spec;
+    }
+
     @Override
     public OcrClient.TrainingResult trainModel(byte[] trainingDataZip) {
         ByteArrayResource zipResource = new ByteArrayResource(trainingDataZip) {
@@ -114,15 +122,10 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
         partHeaders.setContentType(MediaType.parseMediaType("application/zip"));
         body.add("file", new HttpEntity<>(zipResource, partHeaders));
 
-        var spec = trainingRestClient.post()
-                .uri("/train")
-                .contentType(MediaType.MULTIPART_FORM_DATA);
-
-        if (trainingToken != null && !trainingToken.isBlank()) {
-            spec = spec.header("X-Training-Token", trainingToken);
-        }
-
-        TrainingResultJson result = spec
+        TrainingResultJson result = addTrainingAuth(
+                trainingRestClient.post()
+                        .uri("/train")
+                        .contentType(MediaType.MULTIPART_FORM_DATA))
                 .body(body)
                 .retrieve()
                 .body(TrainingResultJson.class);
@@ -143,15 +146,35 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
         partHeaders.setContentType(MediaType.parseMediaType("application/zip"));
         body.add("file", new HttpEntity<>(zipResource, partHeaders));
 
-        var spec = trainingRestClient.post()
-                .uri("/segtrain")
-                .contentType(MediaType.MULTIPART_FORM_DATA);
+        TrainingResultJson result = addTrainingAuth(
+                trainingRestClient.post()
+                        .uri("/segtrain")
+                        .contentType(MediaType.MULTIPART_FORM_DATA))
+                .body(body)
+                .retrieve()
+                .body(TrainingResultJson.class);
 
-        if (trainingToken != null && !trainingToken.isBlank()) {
-            spec = spec.header("X-Training-Token", trainingToken);
-        }
+        if (result == null) return new OcrClient.TrainingResult(null, null, null, null);
+        return new OcrClient.TrainingResult(result.loss(), result.accuracy(), result.cer(), result.epochs());
+    }
 
-        TrainingResultJson result = spec
+    @Override
+    public OcrClient.TrainingResult trainSenderModel(byte[] trainingDataZip, String outputModelPath) {
+        ByteArrayResource zipResource = new ByteArrayResource(trainingDataZip) {
+            @Override
+            public String getFilename() { return "sender-training-data.zip"; }
+        };
+
+        MultiValueMap<String, Object> body = new LinkedMultiValueMap<>();
+        HttpHeaders partHeaders = new HttpHeaders();
+        partHeaders.setContentType(MediaType.parseMediaType("application/zip"));
+        body.add("file", new HttpEntity<>(zipResource, partHeaders));
+        body.add("output_model_path", outputModelPath);
+
+        TrainingResultJson result = addTrainingAuth(
+                trainingRestClient.post()
+                        .uri("/train-sender")
+                        .contentType(MediaType.MULTIPART_FORM_DATA))
                 .body(body)
                 .retrieve()
                 .body(TrainingResultJson.class);
@@ -176,7 +199,8 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
 
     @Override
     public void streamBlocks(String pdfUrl, ScriptType scriptType,
-                              List<OcrRegion> regions, Consumer<OcrStreamEvent> handler) {
+                              List<OcrRegion> regions, @Nullable String senderModelPath,
+                              Consumer<OcrStreamEvent> handler) {
         String body;
         try {
             var requestMap = new java.util.LinkedHashMap<String, Object>();
@@ -186,6 +210,9 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
             if (regions != null && !regions.isEmpty()) {
                 requestMap.put("regions", regions);
             }
+            if (senderModelPath != null) {
+                requestMap.put("senderModelPath", senderModelPath);
+            }
             body = NDJSON_MAPPER.writeValueAsString(requestMap);
         } catch (IOException e) {
             throw new RuntimeException("Failed to serialize OCR request", e);
@@ -204,7 +231,12 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
 
             if (response.statusCode() == 404) {
                 log.info("OCR service does not support /ocr/stream (404), falling back to /ocr");
-                OcrClient.super.streamBlocks(pdfUrl, scriptType, regions, handler);
+                List<OcrBlockResult> allBlocks = extractBlocks(pdfUrl, scriptType);
+                handler.accept(new OcrStreamEvent.Start(0));
+                for (OcrBlockResult block : allBlocks) {
+                    handler.accept(new OcrStreamEvent.Page(block.pageNumber(), List.of(block)));
+                }
+                handler.accept(new OcrStreamEvent.Done(allBlocks.size(), 0));
                 return;
             }
 
@@ -232,6 +264,8 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
                 switch (type) {
                     case "start" -> handler.accept(
                             new OcrStreamEvent.Start(node.path("totalPages").asInt()));
+                    case "preprocessing" -> handler.accept(
+                            new OcrStreamEvent.Preprocessing(node.path("pageNumber").asInt()));
                     case "page" -> {
                         int pageNumber = node.path("pageNumber").asInt();
                         List<OcrBlockResult> blocks = NDJSON_MAPPER.convertValue(

backend/src/main/java/org/raddatz/familienarchiv/service/SenderModelService.java

@@ -0,0 +1,234 @@
+package org.raddatz.familienarchiv.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.exception.DomainException;
+import org.raddatz.familienarchiv.exception.ErrorCode;
+import org.raddatz.familienarchiv.model.OcrTrainingRun;
+import org.raddatz.familienarchiv.model.SenderModel;
+import org.raddatz.familienarchiv.model.TrainingStatus;
+import org.raddatz.familienarchiv.repository.OcrTrainingRunRepository;
+import org.raddatz.familienarchiv.repository.SenderModelRepository;
+import org.raddatz.familienarchiv.repository.TranscriptionBlockRepository;
+import org.slf4j.MDC;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Lazy;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.support.TransactionTemplate;
+
+import java.io.ByteArrayOutputStream;
+import java.time.Instant;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.UUID;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class SenderModelService {
+
+    private final SenderModelRepository senderModelRepository;
+    private final TranscriptionBlockRepository blockRepository;
+    private final OcrTrainingRunRepository trainingRunRepository;
+    private final OcrClient ocrClient;
+    private final TransactionTemplate txTemplate;
+    private final TrainingDataExportService trainingDataExportService;
+    private final PersonService personService;
+
+    // Self-reference through the Spring proxy so @Async is honoured on self-calls.
+    @Lazy
+    @Autowired
+    private SenderModelService self;
+
+    @Value("${ocr.sender-model.activation-threshold:100}")
+    private int activationThreshold;
+
+    @Value("${ocr.sender-model.retrain-delta:50}")
+    private int retrainDelta;
+
+    /** Returns the model path if a trained sender model exists for this person. */
+    public Optional<String> maybeGetModelPath(UUID personId) {
+        return senderModelRepository.findByPersonId(personId)
+                .map(SenderModel::getModelPath);
+    }
+
+    public List<SenderModel> getAllSenderModels() {
+        return senderModelRepository.findAll();
+    }
+
+    public OcrTrainingRun triggerManualSenderTraining(UUID personId) {
+        personService.getById(personId);
+        long correctedLines = blockRepository.countManualKurrentBlocksByPerson(personId);
+        boolean runNow = runOrQueueSenderTraining(personId, (int) correctedLines);
+        TrainingStatus targetStatus = runNow ? TrainingStatus.RUNNING : TrainingStatus.QUEUED;
+        OcrTrainingRun run = trainingRunRepository.findFirstByPersonIdAndStatus(personId, targetStatus)
+                .orElseThrow(() -> DomainException.internal(
+                        ErrorCode.OCR_TRAINING_CONFLICT,
+                        "Expected " + targetStatus + " run for person " + personId));
+        if (runNow) {
+            self.runSenderTraining(personId);
+        }
+        return run;
+    }
+
+    @Async
+    public void runSenderTraining(UUID personId) {
+        long correctedLines = blockRepository.countManualKurrentBlocksByPerson(personId);
+        triggerSenderTraining(personId, (int) correctedLines);
+    }
+
+    /**
+     * Called after every MANUAL block save for HANDWRITING_KURRENT documents.
+     * Checks activation and retrain thresholds; enqueues or starts sender training when met.
+     */
+    @Async
+    public void checkAndTriggerTraining(UUID personId) {
+        long correctedLines = blockRepository.countManualKurrentBlocksByPerson(personId);
+        Optional<SenderModel> existing = senderModelRepository.findByPersonId(personId);
+
+        boolean shouldActivate = existing.isEmpty() && correctedLines >= activationThreshold;
+        boolean shouldRetrain = existing.isPresent()
+                && (correctedLines - existing.get().getCorrectedLinesAtTraining()) >= retrainDelta;
+
+        if (!shouldActivate && !shouldRetrain) {
+            return;
+        }
+
+        log.info("Sender training threshold met for person {} (correctedLines={}, activate={}, retrain={})",
+                personId, correctedLines, shouldActivate, shouldRetrain);
+
+        boolean runNow = runOrQueueSenderTraining(personId, (int) correctedLines);
+        if (runNow) {
+            triggerSenderTraining(personId, (int) correctedLines);
+        }
+    }
+
+    /**
+     * Atomically checks the queue state and either creates a RUNNING row (returns true) or a
+     * QUEUED row (returns false). All three operations — idle check, duplicate-queue guard, and
+     * RUNNING row creation — happen in one transaction, eliminating the race window that would
+     * otherwise exist between the check and a separate RUNNING row creation.
+     */
+    @Transactional
+    public boolean runOrQueueSenderTraining(UUID personId, int correctedLines) {
+        if (trainingRunRepository.existsByPersonIdAndStatus(personId, TrainingStatus.QUEUED)) {
+            log.info("Sender training already queued for person {} — skipping duplicate trigger", personId);
+            return false;
+        }
+
+        if (trainingRunRepository.findFirstByStatus(TrainingStatus.RUNNING).isPresent()) {
+            int blockCount = (int) blockRepository.countManualKurrentBlocksByPerson(personId);
+            trainingRunRepository.save(OcrTrainingRun.builder()
+                    .status(TrainingStatus.QUEUED)
+                    .personId(personId)
+                    .blockCount(blockCount)
+                    .documentCount(0)
+                    .modelName("sender_" + personId)
+                    .build());
+            log.info("Queued sender training for person {} — training already running", personId);
+            return false;
+        }
+
+        long blockCount = blockRepository.countManualKurrentBlocksByPerson(personId);
+        trainingRunRepository.save(OcrTrainingRun.builder()
+                .status(TrainingStatus.RUNNING)
+                .personId(personId)
+                .blockCount((int) blockCount)
+                .documentCount(0)
+                .modelName("sender_" + personId)
+                .build());
+        return true;
+    }
+
+    /**
+     * Executes sender training synchronously. Caller must run this on a background thread.
+     * The RUNNING row is expected to already exist — created atomically by
+     * runOrQueueSenderTraining (for new runs) or by promoteNextQueuedRun (for promoted runs).
+     */
+    public void triggerSenderTraining(UUID personId, int correctedLines) {
+        String outputModelPath = "/app/models/sender_" + personId + ".mlmodel";
+
+        OcrTrainingRun run = Objects.requireNonNull(txTemplate.execute(status ->
+                trainingRunRepository.findFirstByPersonIdAndStatus(personId, TrainingStatus.RUNNING)
+                        .orElseThrow(() -> DomainException.internal(
+                                ErrorCode.OCR_TRAINING_CONFLICT,
+                                "Expected RUNNING row for person " + personId + " but none found"))));
+
+        String runId = run.getId().toString();
+        MDC.put("trainingRunId", runId);
+        log.info("Started sender training run {} for person {}", runId, personId);
+
+        try {
+            byte[] zipBytes = exportSenderData(personId);
+            log.info("[trainingRun={}] Sending {} bytes to OCR service for sender training", runId, zipBytes.length);
+            OcrClient.TrainingResult result = ocrClient.trainSenderModel(zipBytes, outputModelPath);
+
+            txTemplate.execute(status -> {
+                SenderModel model = senderModelRepository.findByPersonId(personId)
+                        .orElseGet(() -> SenderModel.builder().personId(personId).build());
+                model.setModelPath(outputModelPath);
+                model.setCer(result.cer());
+                model.setAccuracy(result.accuracy());
+                model.setCorrectedLinesAtTraining(correctedLines);
+                senderModelRepository.save(model);
+
+                run.setStatus(TrainingStatus.DONE);
+                run.setCompletedAt(Instant.now());
+                run.setCer(result.cer());
+                run.setAccuracy(result.accuracy());
+                run.setEpochs(result.epochs());
+                trainingRunRepository.save(run);
+                log.info("[trainingRun={}] Sender training completed — cer={}", runId, result.cer());
+                return null;
+            });
+        } catch (Exception e) {
+            txTemplate.execute(status -> {
+                run.setStatus(TrainingStatus.FAILED);
+                run.setErrorMessage(e.getMessage());
+                run.setCompletedAt(Instant.now());
+                trainingRunRepository.save(run);
+                log.error("[trainingRun={}] Sender training failed: {}", runId, e.getMessage(), e);
+                return null;
+            });
+        } finally {
+            MDC.remove("trainingRunId");
+            promoteNextQueuedRun();
+        }
+    }
+
+    private byte[] exportSenderData(UUID personId) throws java.io.IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        trainingDataExportService.exportForSender(personId).writeTo(baos);
+        return baos.toByteArray();
+    }
+
+    /**
+     * Promotes the oldest QUEUED sender run to RUNNING and triggers its training.
+     * Called in the finally block of triggerSenderTraining, creating a sequential chain:
+     * each run promotes the next only after it fully completes (success or failure).
+     *
+     * This is intentionally tail-recursive via the @Async thread: the same thread holds the
+     * full queue drain, serialising all sender training runs naturally without an external
+     * scheduler. With N queued runs the thread stays occupied for N sequential trainings —
+     * acceptable because the @Async executor is dedicated to long-running background work.
+     */
+    private void promoteNextQueuedRun() {
+        Optional<OcrTrainingRun> queuedOpt = txTemplate.execute(status ->
+                trainingRunRepository.findFirstByStatusOrderByCreatedAtAsc(TrainingStatus.QUEUED)
+                        .map(queued -> {
+                            queued.setStatus(TrainingStatus.RUNNING);
+                            return trainingRunRepository.save(queued);
+                        }));
+
+        if (queuedOpt != null && queuedOpt.isPresent()) {
+            OcrTrainingRun promoted = queuedOpt.get();
+            log.info("Promoting queued sender training run {} for person {}", promoted.getId(), promoted.getPersonId());
+            long freshCount = blockRepository.countManualKurrentBlocksByPerson(promoted.getPersonId());
+            triggerSenderTraining(promoted.getPersonId(), (int) freshCount);
+        }
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java

@@ -1,30 +1,52 @@
 package org.raddatz.familienarchiv.service;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
+import org.raddatz.familienarchiv.dto.TagTreeNodeDTO;
+import org.raddatz.familienarchiv.dto.TagUpdateDTO;
+import org.raddatz.familienarchiv.exception.DomainException;
+import org.raddatz.familienarchiv.exception.ErrorCode;
 import org.raddatz.familienarchiv.model.Tag;
 import org.raddatz.familienarchiv.repository.TagRepository;
-import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
-import org.springframework.web.server.ResponseStatusException;
+import org.springframework.util.StringUtils;
 
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 
 @Service
 @RequiredArgsConstructor
+@Slf4j
 public class TagService {
 
+    // These 10 color tokens are the fixed palette.
+    // Keep in sync with the --c-tag-* tokens defined in frontend/src/routes/layout.css.
+    static final Set<String> ALLOWED_TAG_COLORS = Set.of(
+            "sage", "sienna", "amber", "slate", "violet",
+            "rose", "cobalt", "moss", "sand", "coral"
+    );
+
     private final TagRepository tagRepository;
 
     public List<Tag> search(String query) {
-        return tagRepository.findByNameContainingIgnoreCase(query);
+        List<Tag> matched = tagRepository.findByNameContainingIgnoreCase(query);
+        if (matched.isEmpty()) return matched;
+        return enrichWithRelatives(matched);
     }
 
     public Tag getById(UUID id) {
         return tagRepository.findById(id)
-                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND, "Tag nicht gefunden"));
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.TAG_NOT_FOUND, "Tag not found: " + id));
     }
 
     public Tag findOrCreate(String name) {
@@ -34,9 +56,22 @@ public class TagService {
     }
 
     @Transactional
-    public Tag update(UUID id, String newName) {
+    public Tag update(UUID id, TagUpdateDTO dto) {
         Tag tag = getById(id);
-        tag.setName(newName);
+
+        if (dto.parentId() != null) {
+            validateNoSelfReference(id, dto.parentId());
+            validateNoAncestorCycle(id, dto.parentId());
+            getById(dto.parentId()); // ensure parent exists
+        }
+
+        if (dto.color() != null) {
+            validateColor(dto.color());
+        }
+
+        tag.setName(dto.name());
+        tag.setParentId(dto.parentId());
+        tag.setColor(dto.color());
         return tagRepository.save(tag);
     }
 
@@ -44,4 +79,175 @@ public class TagService {
     public void delete(UUID id) {
         tagRepository.delete(getById(id));
     }
+
+    @Transactional
+    public Tag mergeTags(UUID sourceId, UUID targetId) {
+        validateNotSelf(sourceId, targetId);
+        Tag source = getById(sourceId);
+        Tag target = getById(targetId);
+        log.info("Merging tag '{}' ({}) into '{}' ({})", source.getName(), sourceId, target.getName(), targetId);
+        validateNotDescendant(sourceId, targetId);
+        transferDocuments(sourceId, targetId);
+        tagRepository.reparentChildren(sourceId, targetId);
+        tagRepository.deleteById(sourceId);
+        return target;
+    }
+
+    @Transactional
+    public void deleteWithDescendants(UUID id) {
+        log.info("Deleting subtree rooted at {}", id);
+        getById(id);
+        List<UUID> ids = tagRepository.findDescendantIds(id);
+        if (!ids.isEmpty()) tagRepository.deleteDocumentTagsByTagIds(ids);
+        tagRepository.deleteAllById(ids);
+        log.info("Deleted subtree rooted at {}, {} nodes", id, ids.size());
+    }
+
+    /**
+     * Sets the effective (inherited) color on child tags that have no color of their own.
+     * Colors are stored only on root-level tags; children inherit the parent's color.
+     * Parent tags are batch-loaded in a single query. Safe to call on detached entities.
+     */
+    public void resolveEffectiveColors(Collection<Tag> tags) {
+        if (tags == null || tags.isEmpty()) return;
+
+        Set<UUID> parentIdsNeeded = tags.stream()
+                .filter(t -> t.getColor() == null && t.getParentId() != null)
+                .map(Tag::getParentId)
+                .collect(Collectors.toSet());
+
+        if (parentIdsNeeded.isEmpty()) return;
+
+        Map<UUID, String> parentColors = tagRepository.findAllById(parentIdsNeeded)
+                .stream()
+                .filter(p -> p.getColor() != null)
+                .collect(Collectors.toMap(Tag::getId, Tag::getColor));
+
+        tags.forEach(tag -> {
+            if (tag.getColor() == null && tag.getParentId() != null) {
+                String resolved = parentColors.get(tag.getParentId());
+                if (resolved != null) {
+                    tag.setColor(resolved);
+                }
+            }
+        });
+    }
+
+    /**
+     * For each tag name, returns the set of that tag's ID plus all descendant IDs.
+     * Used by DocumentService to expand selected filter tags before applying AND/OR logic.
+     */
+    public List<Set<UUID>> expandTagNamesToDescendantIdSets(List<String> tagNames) {
+        if (tagNames == null || tagNames.isEmpty()) return List.of();
+        return tagNames.stream()
+                .filter(StringUtils::hasText)
+                .map(name -> (Set<UUID>) new HashSet<>(tagRepository.findDescendantIdsByName(name.trim())))
+                .toList();
+    }
+
+    /**
+     * Returns all tags assembled into a tree with document counts per node.
+     * Uses a single aggregate query to avoid N+1 behaviour.
+     * NOTE: document counts are global per tag, not scoped to any search filter.
+     * The tree endpoint is only used for the admin sidebar, so this is intentional.
+     */
+    public List<TagTreeNodeDTO> getTagTree() {
+        List<Tag> all = tagRepository.findAll();
+        Map<UUID, Long> counts = tagRepository.findDocumentCountsPerTag().stream()
+                .collect(Collectors.toMap(
+                        TagRepository.TagCount::getTagId,
+                        TagRepository.TagCount::getCount
+                ));
+        return buildTree(all, counts);
+    }
+
+    // ─── private helpers ─────────────────────────────────────────────────────
+
+    // Each matched tag issues 1 CTE query (findDescendantIds or findAncestorIds) + 1 batch
+    // fetch for extras. Typical queries match 1–3 tags at depth ≤ 4, so 3–5 queries total.
+    private List<Tag> enrichWithRelatives(List<Tag> matched) {
+        Set<UUID> matchedIds = matched.stream().map(Tag::getId).collect(Collectors.toSet());
+        Set<UUID> extraIds = new HashSet<>();
+
+        for (Tag tag : matched) {
+            if (tag.getParentId() == null) {
+                extraIds.addAll(tagRepository.findDescendantIds(tag.getId()));
+            } else {
+                extraIds.addAll(tagRepository.findAncestorIds(tag.getId()));
+            }
+        }
+        extraIds.removeAll(matchedIds);
+
+        List<Tag> result = new ArrayList<>(matched);
+        if (!extraIds.isEmpty()) {
+            result.addAll(tagRepository.findAllById(extraIds));
+        }
+        resolveEffectiveColors(result);
+        return result;
+    }
+
+    private void validateNotSelf(UUID sourceId, UUID targetId) {
+        if (sourceId.equals(targetId)) {
+            throw DomainException.badRequest(ErrorCode.TAG_MERGE_SELF,
+                    "Source and target must not be the same tag: " + sourceId);
+        }
+    }
+
+    private void validateNotDescendant(UUID sourceId, UUID targetId) {
+        List<UUID> descendants = tagRepository.findDescendantIds(sourceId);
+        if (descendants.contains(targetId)) {
+            throw DomainException.badRequest(ErrorCode.TAG_MERGE_INVALID_TARGET,
+                    "Target " + targetId + " is a descendant of source " + sourceId);
+        }
+    }
+
+    private void transferDocuments(UUID sourceId, UUID targetId) {
+        tagRepository.reassignDocumentTags(sourceId, targetId);
+        tagRepository.deleteDocumentTagsByTagId(sourceId);
+    }
+
+    private void validateNoSelfReference(UUID tagId, UUID proposedParentId) {
+        if (tagId.equals(proposedParentId)) {
+            throw DomainException.badRequest(ErrorCode.TAG_CYCLE_DETECTED,
+                    "A tag cannot be its own parent: " + tagId);
+        }
+    }
+
+    private void validateNoAncestorCycle(UUID tagId, UUID proposedParentId) {
+        // TOCTOU note: concurrent admin writes could both pass this check and create a
+        // multi-node cycle. This is intentionally not locked because: (a) the endpoint
+        // requires ADMIN_TAG permission so concurrency is rare, (b) the DB-level
+        // CHECK (parent_id != id) prevents infinite self-loops as a hard backstop,
+        // and (c) the window is microseconds. Do NOT add a pessimistic lock here.
+        List<UUID> ancestors = tagRepository.findAncestorIds(proposedParentId);
+        if (ancestors.contains(tagId)) {
+            throw DomainException.badRequest(ErrorCode.TAG_CYCLE_DETECTED,
+                    "Assigning parent " + proposedParentId + " to tag " + tagId + " would create a cycle");
+        }
+    }
+
+    private void validateColor(String color) {
+        if (!ALLOWED_TAG_COLORS.contains(color)) {
+            throw DomainException.badRequest(ErrorCode.INVALID_TAG_COLOR,
+                    "Color '" + color + "' is not in the allowed palette");
+        }
+    }
+
+    private List<TagTreeNodeDTO> buildTree(List<Tag> tags, Map<UUID, Long> counts) {
+        Map<UUID, TagTreeNodeDTO> nodeById = new LinkedHashMap<>();
+        for (Tag tag : tags) {
+            int documentCount = counts.getOrDefault(tag.getId(), 0L).intValue();
+            nodeById.put(tag.getId(), new TagTreeNodeDTO(
+                    tag.getId(), tag.getName(), tag.getColor(), documentCount,
+                    new ArrayList<>(), tag.getParentId()
+            ));
+        }
+        for (TagTreeNodeDTO node : nodeById.values()) {
+            if (node.parentId() != null) {
+                TagTreeNodeDTO parent = nodeById.get(node.parentId());
+                if (parent != null) parent.children().add(node);
+            }
+        }
+        return nodeById.values().stream().filter(n -> n.parentId() == null).toList();
+    }
 }

backend/src/main/java/org/raddatz/familienarchiv/service/ThumbnailAsyncRunner.java

@@ -0,0 +1,92 @@
+package org.raddatz.familienarchiv.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.model.Document;
+import org.raddatz.familienarchiv.repository.DocumentRepository;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.support.TransactionSynchronization;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import java.util.Optional;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * Bridges document upload paths to asynchronous thumbnail generation. Use
+ * {@link #dispatchAfterCommit(UUID)} from inside {@code @Transactional} service methods —
+ * it registers a post-commit hook so the async task only fires when the surrounding
+ * transaction actually commits, and is silently skipped on rollback. Mirrors
+ * {@link org.raddatz.familienarchiv.audit.AuditService#logAfterCommit}.
+ */
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class ThumbnailAsyncRunner {
+
+    private final DocumentRepository documentRepository;
+    private final ThumbnailService thumbnailService;
+
+    /** Per-document timeout for the whole generate() call — defense against corrupt PDFs. */
+    private long generateTimeoutSeconds = 30L;
+
+    /**
+     * Registers a post-commit hook that triggers asynchronous thumbnail generation for the
+     * given document. When no transaction is active the task is dispatched immediately.
+     * Safe to call from inside {@code @Transactional} service methods.
+     */
+    public void dispatchAfterCommit(UUID documentId) {
+        if (TransactionSynchronizationManager.isSynchronizationActive()) {
+            TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
+                @Override
+                public void afterCommit() {
+                    generateAsync(documentId);
+                }
+            });
+        } else {
+            generateAsync(documentId);
+        }
+    }
+
+    /**
+     * Runs thumbnail generation on the {@code thumbnailExecutor} pool, wrapped in a watchdog
+     * timeout so a hung PDFBox render cannot occupy a pool thread indefinitely. Never throws:
+     * all errors and timeouts are logged and swallowed so upload paths are not affected.
+     */
+    @Async("thumbnailExecutor")
+    public void generateAsync(UUID documentId) {
+        Optional<Document> docOpt = documentRepository.findById(documentId);
+        if (docOpt.isEmpty()) {
+            log.warn("Thumbnail generation skipped: document not found id={}", documentId);
+            return;
+        }
+        Document doc = docOpt.get();
+
+        ExecutorService timeoutWorker = Executors.newSingleThreadExecutor(r -> {
+            Thread t = new Thread(r, "Thumbnail-Render-" + documentId);
+            t.setDaemon(true);
+            return t;
+        });
+        try {
+            Future<ThumbnailService.Outcome> future = timeoutWorker.submit(
+                    () -> thumbnailService.generate(doc));
+            try {
+                future.get(generateTimeoutSeconds, TimeUnit.SECONDS);
+            } catch (TimeoutException e) {
+                future.cancel(true);
+                log.warn("Thumbnail generation timed out after {}s for doc={}",
+                        generateTimeoutSeconds, documentId);
+            } catch (Exception e) {
+                log.warn("Thumbnail generation errored for doc={} reason={}",
+                        documentId, e.getMessage());
+            }
+        } finally {
+            timeoutWorker.shutdownNow();
+        }
+    }
+}

backend/src/main/java/org/raddatz/familienarchiv/service/ThumbnailBackfillService.java

@@ -0,0 +1,104 @@
+package org.raddatz.familienarchiv.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.exception.DomainException;
+import org.raddatz.familienarchiv.exception.ErrorCode;
+import org.raddatz.familienarchiv.model.Document;
+import org.raddatz.familienarchiv.repository.DocumentRepository;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.util.List;
+
+/**
+ * Sequentially regenerates thumbnails for documents that have a file attached but no
+ * thumbnail yet. Runs on the {@code thumbnailExecutor} pool — single-threaded iteration
+ * is intentional: PDFBox + ImageIO are memory-heavy and we cap peak usage by processing
+ * documents one at a time. Only one backfill can run at a time; concurrent starts are
+ * rejected with {@link ErrorCode#THUMBNAIL_BACKFILL_ALREADY_RUNNING}.
+ */
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class ThumbnailBackfillService {
+
+    public enum State { IDLE, RUNNING, DONE, FAILED }
+
+    public record BackfillStatus(
+            State state,
+            String message,
+            int total,
+            int processed,
+            int skipped,
+            int failed,
+            LocalDateTime startedAt
+    ) {}
+
+    private final DocumentRepository documentRepository;
+    private final ThumbnailService thumbnailService;
+
+    private volatile BackfillStatus currentStatus = new BackfillStatus(
+            State.IDLE, "Kein Backfill gestartet.", 0, 0, 0, 0, null);
+
+    public BackfillStatus getStatus() {
+        return currentStatus;
+    }
+
+    @Async("thumbnailExecutor")
+    public void runBackfillAsync() {
+        if (currentStatus.state() == State.RUNNING) {
+            throw DomainException.conflict(ErrorCode.THUMBNAIL_BACKFILL_ALREADY_RUNNING,
+                    "Thumbnail-Backfill läuft bereits");
+        }
+
+        LocalDateTime startedAt = LocalDateTime.now();
+        List<Document> docs;
+        try {
+            docs = documentRepository.findByFilePathIsNotNullAndThumbnailKeyIsNull();
+        } catch (Exception e) {
+            currentStatus = new BackfillStatus(State.FAILED,
+                    "Backfill fehlgeschlagen: " + e.getMessage(),
+                    0, 0, 0, 0, startedAt);
+            log.warn("Thumbnail backfill aborted before starting: {}", e.getMessage());
+            return;
+        }
+
+        int total = docs.size();
+        currentStatus = new BackfillStatus(State.RUNNING,
+                "Backfill läuft…", total, 0, 0, 0, startedAt);
+        log.info("Thumbnail backfill started: total={}", total);
+
+        int processed = 0;
+        int skipped = 0;
+        int failed = 0;
+        for (Document doc : docs) {
+            ThumbnailService.Outcome outcome;
+            try {
+                outcome = thumbnailService.generate(doc);
+            } catch (Exception e) {
+                log.warn("Thumbnail generation failed for doc={} reason={}",
+                        doc.getId(), e.getMessage());
+                outcome = ThumbnailService.Outcome.FAILED;
+            }
+            switch (outcome) {
+                case SUCCESS -> processed++;
+                case SKIPPED -> skipped++;
+                case FAILED -> failed++;
+            }
+            currentStatus = new BackfillStatus(State.RUNNING,
+                    "Backfill läuft…", total, processed, skipped, failed, startedAt);
+        }
+
+        long durationMs = Duration.between(startedAt, LocalDateTime.now()).toMillis();
+        log.info("Thumbnail backfill complete: total={} processed={} skipped={} failed={} durationMs={}",
+                total, processed, skipped, failed, durationMs);
+
+        currentStatus = new BackfillStatus(State.DONE,
+                String.format("Fertig: %d erzeugt, %d übersprungen, %d fehlgeschlagen.",
+                        processed, skipped, failed),
+                total, processed, skipped, failed, startedAt);
+    }
+}