feat(backend): extend conversation endpoint for optional receiverId

When receiverId is omitted, returns all documents where the person is
sender or receiver (single-person mode). Bilateral mode is unchanged.

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

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

@@ -212,7 +212,7 @@ public class DocumentController {
     @GetMapping("/conversation")
     public List<Document> getConversation(
             @RequestParam UUID senderId,
-            @RequestParam UUID receiverId,
+            @RequestParam(required = false) UUID receiverId,
             @RequestParam(required = false) LocalDate from,
             @RequestParam(required = false) LocalDate to,
             @RequestParam(defaultValue = "DESC") String dir) {

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

@@ -60,11 +60,9 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
     @Query("SELECT DISTINCT d FROM Document d " +
             "JOIN d.receivers r " +
             "WHERE " +
-            // Logik: (Sender A an Empfänger B) ODER (Sender B an Empfänger A)
             "((d.sender.id = :person1 AND r.id = :person2) " +
             " OR " +
             " (d.sender.id = :person2 AND r.id = :person1)) " +
-            // UND das Datum stimmt
             "AND d.documentDate BETWEEN :from AND :to")
     List<Document> findConversation(
             @Param("person1") UUID person1,
@@ -73,4 +71,14 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
             @Param("to") LocalDate to,
             Sort sort);
 
+    @Query("SELECT DISTINCT d FROM Document d " +
+            "LEFT JOIN d.receivers r " +
+            "WHERE (d.sender.id = :personId OR r.id = :personId) " +
+            "AND d.documentDate BETWEEN :from AND :to")
+    List<Document> findSinglePersonCorrespondence(
+            @Param("personId") UUID personId,
+            @Param("from") LocalDate from,
+            @Param("to") LocalDate to,
+            Sort sort);
+
 }

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

@@ -328,6 +328,9 @@ public class DocumentService {
     public List<Document> getConversationFiltered(UUID senderId, UUID receiverId, LocalDate from, LocalDate to, Sort sort) {
         LocalDate dateFrom = (from != null) ? from : LocalDate.parse("0000-01-01");
         LocalDate dateTo = (to != null) ? to : LocalDate.now();
+        if (receiverId == null) {
+            return documentRepository.findSinglePersonCorrespondence(senderId, dateFrom, dateTo, sort);
+        }
         return documentRepository.findConversation(senderId, receiverId, dateFrom, dateTo, sort);
     }
 

backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java

@@ -1244,4 +1244,33 @@ class DocumentServiceTest {
         assertThat(captor.getValue().getSort())
                 .isEqualTo(Sort.by(Sort.Direction.DESC, "updatedAt"));
     }
+
+    // ─── getConversationFiltered (single-person mode) ─────────────────────────
+
+    @Test
+    void getConversationFiltered_callsSinglePersonQuery_whenReceiverIdIsNull() {
+        UUID personId = UUID.randomUUID();
+        Sort sort = Sort.by(Sort.Direction.DESC, "documentDate");
+        when(documentRepository.findSinglePersonCorrespondence(eq(personId), any(), any(), eq(sort)))
+                .thenReturn(List.of());
+
+        documentService.getConversationFiltered(personId, null, null, null, sort);
+
+        verify(documentRepository).findSinglePersonCorrespondence(eq(personId), any(), any(), eq(sort));
+        verify(documentRepository, never()).findConversation(any(), any(), any(), any(), any());
+    }
+
+    @Test
+    void getConversationFiltered_callsBilateralQuery_whenReceiverIdIsSet() {
+        UUID senderId = UUID.randomUUID();
+        UUID receiverId = UUID.randomUUID();
+        Sort sort = Sort.by(Sort.Direction.DESC, "documentDate");
+        when(documentRepository.findConversation(eq(senderId), eq(receiverId), any(), any(), eq(sort)))
+                .thenReturn(List.of());
+
+        documentService.getConversationFiltered(senderId, receiverId, null, null, sort);
+
+        verify(documentRepository).findConversation(eq(senderId), eq(receiverId), any(), any(), eq(sort));
+        verify(documentRepository, never()).findSinglePersonCorrespondence(any(), any(), any(), any());
+    }
 }