feat(backend): dispatch thumbnail generation from DocumentService upload paths

All four upload code paths (storeDocument, createDocument, updateDocument,
attachFile) now call thumbnailAsyncRunner.dispatchAfterCommit(id) after
the document save. createDocument and updateDocument only dispatch when a
file was actually provided/replaced.

The dispatch is afterCommit-safe: if the surrounding @Transactional
method rolls back, no thumbnail is generated for a document that never
reached the DB.

Refs #307

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

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

@@ -64,6 +64,7 @@ public class DocumentService {
     private final AuditService auditService;
     private final TranscriptionBlockQueryService transcriptionBlockQueryService;
     private final AuditLogQueryService auditLogQueryService;
+    private final ThumbnailAsyncRunner thumbnailAsyncRunner;
 
     public record StoreResult(Document document, boolean isNew) {}
 
@@ -125,6 +126,7 @@ public class DocumentService {
         if (wasPlaceholder) {
             auditService.logAfterCommit(AuditKind.FILE_UPLOADED, actorId, saved.getId(), null);
         }
+        thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
         return new StoreResult(saved, isNew);
     }
 
@@ -187,7 +189,8 @@ 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());
@@ -197,6 +200,9 @@ public class DocumentService {
 
         Document finalDoc = documentRepository.save(doc);
         documentVersionService.recordVersion(finalDoc);
+        if (fileUploaded) {
+            thumbnailAsyncRunner.dispatchAfterCommit(finalDoc.getId());
+        }
         return finalDoc;
     }
 
@@ -249,7 +255,8 @@ 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());
@@ -268,6 +275,10 @@ public class DocumentService {
             auditService.logAfterCommit(AuditKind.METADATA_UPDATED, actorId, saved.getId(), null);
         }
 
+        if (fileReplaced) {
+            thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
+        }
+
         return saved;
     }
 
@@ -329,6 +340,7 @@ public class DocumentService {
         }
         Document saved = documentRepository.save(doc);
         documentVersionService.recordVersion(saved);
+        thumbnailAsyncRunner.dispatchAfterCommit(saved.getId());
         if (wasPlaceholder) {
             auditService.logAfterCommit(AuditKind.FILE_UPLOADED, actorId, saved.getId(), null);
         }

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

@@ -55,6 +55,7 @@ class DocumentServiceTest {
     @Mock AuditService auditService;
     @Mock AuditLogQueryService auditLogQueryService;
     @Mock TranscriptionBlockQueryService transcriptionBlockQueryService;
+    @Mock ThumbnailAsyncRunner thumbnailAsyncRunner;
     @InjectMocks DocumentService documentService;
 
     // ─── deleteDocument ───────────────────────────────────────────────────────
@@ -257,6 +258,107 @@ class DocumentServiceTest {
         verify(documentVersionService).recordVersion(any(Document.class));
     }
 
+    // ─── thumbnail dispatch ───────────────────────────────────────────────────
+
+    @Test
+    void storeDocument_dispatchesThumbnailAfterSave() throws Exception {
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("file", "new.pdf", "application/pdf", new byte[]{1});
+        UUID savedId = UUID.randomUUID();
+        Document saved = Document.builder().id(savedId).originalFilename("new.pdf").build();
+        when(documentRepository.findFirstByOriginalFilename("new.pdf")).thenReturn(Optional.empty());
+        when(documentRepository.save(any())).thenReturn(saved);
+        when(fileService.uploadFile(any(), any())).thenReturn(new FileService.UploadResult("documents/new.pdf", "hash"));
+
+        documentService.storeDocument(file, null);
+
+        verify(thumbnailAsyncRunner, times(1)).dispatchAfterCommit(savedId);
+    }
+
+    @Test
+    void createDocument_dispatchesThumbnail_onlyWhenFileProvided() throws Exception {
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        dto.setTitle("No file");
+        UUID savedId = UUID.randomUUID();
+        Document saved = Document.builder().id(savedId).title("No file")
+                .originalFilename("No file").status(DocumentStatus.PLACEHOLDER).build();
+        when(documentRepository.save(any())).thenReturn(saved);
+        when(documentRepository.findById(any())).thenReturn(Optional.of(saved));
+
+        documentService.createDocument(dto, null);
+
+        verifyNoInteractions(thumbnailAsyncRunner);
+    }
+
+    @Test
+    void createDocument_dispatchesThumbnail_whenFileProvided() throws Exception {
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        dto.setTitle("With file");
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("file", "scan.pdf", "application/pdf", new byte[]{1});
+        UUID savedId = UUID.randomUUID();
+        Document saved = Document.builder().id(savedId).title("With file")
+                .originalFilename("scan.pdf").status(DocumentStatus.PLACEHOLDER).build();
+        when(documentRepository.save(any())).thenReturn(saved);
+        when(documentRepository.findById(any())).thenReturn(Optional.of(saved));
+        when(fileService.uploadFile(any(), any()))
+                .thenReturn(new FileService.UploadResult("documents/scan.pdf", "hash"));
+
+        documentService.createDocument(dto, file);
+
+        verify(thumbnailAsyncRunner, times(1)).dispatchAfterCommit(savedId);
+    }
+
+    @Test
+    void updateDocument_dispatchesThumbnail_onlyWhenFileReplaced() throws Exception {
+        UUID id = UUID.randomUUID();
+        Document existing = Document.builder()
+                .id(id).title("Doc").originalFilename("old.pdf")
+                .status(DocumentStatus.UPLOADED).build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(existing));
+        when(documentRepository.save(any())).thenReturn(existing);
+
+        documentService.updateDocument(id, new DocumentUpdateDTO(), null, null);
+
+        verifyNoInteractions(thumbnailAsyncRunner);
+    }
+
+    @Test
+    void updateDocument_dispatchesThumbnail_whenNewFileProvided() throws Exception {
+        UUID id = UUID.randomUUID();
+        Document existing = Document.builder()
+                .id(id).title("Doc").originalFilename("old.pdf")
+                .status(DocumentStatus.UPLOADED).build();
+        org.springframework.mock.web.MockMultipartFile newFile =
+                new org.springframework.mock.web.MockMultipartFile("file", "new.pdf", "application/pdf", new byte[]{1});
+        when(documentRepository.findById(id)).thenReturn(Optional.of(existing));
+        when(documentRepository.save(any())).thenReturn(existing);
+        when(fileService.uploadFile(any(), any()))
+                .thenReturn(new FileService.UploadResult("documents/new.pdf", "hash"));
+
+        documentService.updateDocument(id, new DocumentUpdateDTO(), newFile, null);
+
+        verify(thumbnailAsyncRunner, times(1)).dispatchAfterCommit(id);
+    }
+
+    @Test
+    void attachFile_dispatchesThumbnailAfterSave() throws Exception {
+        UUID id = UUID.randomUUID();
+        Document existing = Document.builder()
+                .id(id).title("Placeholder").originalFilename("placeholder")
+                .status(DocumentStatus.PLACEHOLDER).build();
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("file", "scan.pdf", "application/pdf", new byte[]{1});
+        when(documentRepository.findById(id)).thenReturn(Optional.of(existing));
+        when(documentRepository.save(any())).thenReturn(existing);
+        when(fileService.uploadFile(any(), any()))
+                .thenReturn(new FileService.UploadResult("documents/scan.pdf", "hash"));
+
+        documentService.attachFile(id, file, null);
+
+        verify(thumbnailAsyncRunner, times(1)).dispatchAfterCommit(id);
+    }
+
     // ─── storeDocument ───────────────────────────────────────────────────────
 
     @Test