feat(transcription): add source/reviewed fields for training pipeline

- BlockSource enum: MANUAL, OCR
- V26 migration adds source + reviewed columns to transcription_blocks
- OcrService sets source=OCR when creating blocks
- TranscriptionService.reviewBlock() toggles the reviewed flag
- PUT /api/documents/{id}/transcription-blocks/{blockId}/review endpoint
- 5 new tests: reviewBlock toggle/untoggle/notfound, controller,
  OcrService source=OCR verification

The reviewed flag enables the Kraken fine-tuning pipeline: only blocks
marked as reviewed by a human are exported as training data.

Refs #226

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

backend/src/test/java/org/raddatz/familienarchiv/controller/TranscriptionBlockControllerTest.java

@@ -356,4 +356,20 @@ class TranscriptionBlockControllerTest {
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$").isEmpty());
     }
+
+    // ─── PUT .../review ──────────────────────────────────────────────────────
+
+    @Test
+    @WithMockUser(authorities = "WRITE_ALL")
+    void reviewBlock_returns200_withToggledBlock() throws Exception {
+        TranscriptionBlock reviewed = TranscriptionBlock.builder()
+                .id(BLOCK_ID).documentId(DOC_ID).annotationId(UUID.randomUUID())
+                .text("text").sortOrder(0).reviewed(true).build();
+        when(transcriptionService.reviewBlock(DOC_ID, BLOCK_ID)).thenReturn(reviewed);
+
+        mockMvc.perform(put("/api/documents/{documentId}/transcription-blocks/{blockId}/review",
+                        DOC_ID, BLOCK_ID))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.reviewed").value(true));
+    }
 }

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

@@ -6,6 +6,7 @@ import org.mockito.ArgumentCaptor;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+import org.mockito.ArgumentCaptor;
 import org.raddatz.familienarchiv.dto.CreateAnnotationDTO;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
@@ -173,4 +174,32 @@ class OcrServiceTest {
         verify(annotationService, times(2)).createOcrAnnotation(
                 eq(docId), any(CreateAnnotationDTO.class), eq(userId), eq("hash123"), any());
     }
+
+    @Test
+    void startOcr_setsBlockSourceToOcr() {
+        UUID docId = UUID.randomUUID();
+        UUID userId = UUID.randomUUID();
+        Document doc = Document.builder().id(docId).status(DocumentStatus.UPLOADED)
+                .filePath("documents/test.pdf").fileHash("hash123")
+                .scriptType(ScriptType.TYPEWRITER).build();
+        OcrBlockResult block = new OcrBlockResult(0, 0.1, 0.1, 0.8, 0.04, null, "Test");
+
+        when(documentService.getDocumentById(docId)).thenReturn(doc);
+        when(ocrHealthClient.isHealthy()).thenReturn(true);
+        when(transcriptionService.listBlocks(docId)).thenReturn(List.of());
+        when(ocrClient.extractBlocks(any(), any())).thenReturn(List.of(block));
+        when(ocrJobRepository.save(any())).thenAnswer(inv -> {
+            OcrJob job = inv.getArgument(0);
+            job.setId(UUID.randomUUID());
+            return job;
+        });
+        DocumentAnnotation ann = DocumentAnnotation.builder().id(UUID.randomUUID()).build();
+        when(annotationService.createOcrAnnotation(any(), any(), any(), any(), any())).thenReturn(ann);
+
+        ocrService.startOcr(docId, null, userId);
+
+        ArgumentCaptor<TranscriptionBlock> captor = ArgumentCaptor.forClass(TranscriptionBlock.class);
+        verify(blockRepository).save(captor.capture());
+        assertThat(captor.getValue().getSource()).isEqualTo(BlockSource.OCR);
+    }
 }

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

@@ -243,4 +243,47 @@ class TranscriptionServiceTest {
 
         assertThat(transcriptionService.listBlocks(docId)).containsExactly(b);
     }
+
+    // ─── reviewBlock ─────────────────────────────────────────────────────────
+
+    @Test
+    void reviewBlock_setsReviewedTrue() {
+        UUID docId = UUID.randomUUID();
+        UUID blockId = UUID.randomUUID();
+        TranscriptionBlock block = TranscriptionBlock.builder()
+                .id(blockId).documentId(docId).annotationId(UUID.randomUUID())
+                .text("corrected text").sortOrder(0).reviewed(false).build();
+        when(blockRepository.findByIdAndDocumentId(blockId, docId)).thenReturn(Optional.of(block));
+        when(blockRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        TranscriptionBlock result = transcriptionService.reviewBlock(docId, blockId);
+
+        assertThat(result.isReviewed()).isTrue();
+        verify(blockRepository).save(block);
+    }
+
+    @Test
+    void reviewBlock_togglesReviewedFalse_whenAlreadyReviewed() {
+        UUID docId = UUID.randomUUID();
+        UUID blockId = UUID.randomUUID();
+        TranscriptionBlock block = TranscriptionBlock.builder()
+                .id(blockId).documentId(docId).annotationId(UUID.randomUUID())
+                .text("corrected text").sortOrder(0).reviewed(true).build();
+        when(blockRepository.findByIdAndDocumentId(blockId, docId)).thenReturn(Optional.of(block));
+        when(blockRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        TranscriptionBlock result = transcriptionService.reviewBlock(docId, blockId);
+
+        assertThat(result.isReviewed()).isFalse();
+    }
+
+    @Test
+    void reviewBlock_throwsNotFound_whenBlockMissing() {
+        UUID docId = UUID.randomUUID();
+        UUID blockId = UUID.randomUUID();
+        when(blockRepository.findByIdAndDocumentId(blockId, docId)).thenReturn(Optional.empty());
+
+        assertThatThrownBy(() -> transcriptionService.reviewBlock(docId, blockId))
+                .isInstanceOf(DomainException.class);
+    }
 }