fix(backend): rename users table to app_users

Aligns the auth-account table name with the AppUser entity. The historical
mismatch (table 'users' alongside table 'persons') misled schema-first readers
into assuming the two were related; renaming to 'app_users' makes the
deliberate split between auth accounts and historical persons explicit at the
schema layer.

Scope: the table itself, the users_groups join table, and the three FK columns
whose name was literally 'user_id'. Semantic FK columns (audit_log.actor_id,
notifications.recipient_id, document_versions.editor_id, etc.) keep their
names — the role they describe is the documentation, not the type.

Closes #418. Unblocks #407 (REFACTOR-1).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -104,7 +104,7 @@ public interface AuditLogQueryRepository extends JpaRepository<AuditLog, UUID> {
                 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
+            LEFT JOIN app_users u ON u.id = ag.actor_id
             ORDER BY ag.happened_at DESC
             LIMIT :limit
             """, nativeQuery = true)
@@ -157,7 +157,7 @@ public interface AuditLogQueryRepository extends JpaRepository<AuditLog, UUID> {
                 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
+            LEFT JOIN app_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
@@ -189,7 +189,7 @@ public interface AuditLogQueryRepository extends JpaRepository<AuditLog, UUID> {
                         ORDER BY MAX(a.happened_at) DESC
                     )                                                          AS rn
                 FROM audit_log a
-                LEFT JOIN users u ON u.id = a.actor_id
+                LEFT JOIN app_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

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

@@ -24,7 +24,7 @@ import jakarta.persistence.PrePersist;
 import jakarta.persistence.PreUpdate;
 
 @Entity
-@Table(name = "users")
+@Table(name = "app_users")
 @Data
 @NoArgsConstructor
 @AllArgsConstructor
@@ -69,7 +69,7 @@ public class AppUser {
     private boolean notifyOnMention = false;
 
     @ManyToMany(fetch = FetchType.EAGER)
-    @JoinTable(name = "users_groups", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "group_id"))
+    @JoinTable(name = "app_users_groups", joinColumns = @JoinColumn(name = "app_user_id"), inverseJoinColumns = @JoinColumn(name = "group_id"))
     @Builder.Default
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private Set<UserGroup> groups = new HashSet<>();

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

@@ -71,7 +71,7 @@ public class DocumentComment {
     @JoinTable(
             name = "comment_mentions",
             joinColumns = @JoinColumn(name = "comment_id"),
-            inverseJoinColumns = @JoinColumn(name = "user_id")
+            inverseJoinColumns = @JoinColumn(name = "app_user_id")
     )
     @JsonIgnore
     @Builder.Default

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

@@ -30,7 +30,7 @@ public class PasswordResetToken {
     private UUID id;
 
     @ManyToOne(fetch = FetchType.LAZY)
-    @JoinColumn(name = "user_id", nullable = false)
+    @JoinColumn(name = "app_user_id", nullable = false)
     private AppUser user;
 
     @Column(nullable = false, unique = true, length = 64)