feat(#68): fall back to filename as title when createDocument gets no title

When a document is created without an explicit title (null or blank),
the service now derives the title from the uploaded filename using the
same titleFromFilename() logic already used by storeDocument — stripping
the extension for plain names and formatting structured names as
"Firstname Lastname (DD.MM.YYYY)".

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

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

@@ -108,9 +108,13 @@ public class DocumentService {
                     || (dto.getReceiverIds() != null && !dto.getReceiverIds().isEmpty());
         }
 
+        String titleToUse = (dto.getTitle() != null && !dto.getTitle().isBlank())
+                ? dto.getTitle()
+                : titleFromFilename(filename);
+
         Document doc = Document.builder()
                 .originalFilename(filename)
-                .title(dto.getTitle())
+                .title(titleToUse)
                 .documentDate(dto.getDocumentDate())
                 .location(dto.getLocation())
                 .documentLocation(dto.getDocumentLocation())

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

@@ -467,6 +467,62 @@ class DocumentServiceTest {
         assertThat(captor.getValue().getSender()).isNull();
     }
 
+    // ─── createDocument title fallback ────────────────────────────────────────
+
+    @Test
+    void createDocument_usesTitleFromFilename_whenDtoTitleIsNull() throws Exception {
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        // dto.title is null
+        MockMultipartFile file = new MockMultipartFile("file", "Brief_1965.pdf", "application/pdf", new byte[]{1});
+        Document saved = Document.builder().id(UUID.randomUUID()).title("Brief_1965")
+                .originalFilename("Brief_1965.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("path", "hash"));
+
+        ArgumentCaptor<Document> captor = ArgumentCaptor.forClass(Document.class);
+        documentService.createDocument(dto, file);
+
+        verify(documentRepository, atLeastOnce()).save(captor.capture());
+        assertThat(captor.getAllValues().get(0).getTitle()).isEqualTo("Brief_1965");
+    }
+
+    @Test
+    void createDocument_usesTitleFromFilename_whenDtoTitleIsBlank() throws Exception {
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        dto.setTitle("   ");
+        MockMultipartFile file = new MockMultipartFile("file", "Rechnung_1980.pdf", "application/pdf", new byte[]{1});
+        Document saved = Document.builder().id(UUID.randomUUID()).title("Rechnung_1980")
+                .originalFilename("Rechnung_1980.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("path", "hash"));
+
+        ArgumentCaptor<Document> captor = ArgumentCaptor.forClass(Document.class);
+        documentService.createDocument(dto, file);
+
+        verify(documentRepository, atLeastOnce()).save(captor.capture());
+        assertThat(captor.getAllValues().get(0).getTitle()).isEqualTo("Rechnung_1980");
+    }
+
+    @Test
+    void createDocument_keepsDtoTitle_whenProvided() throws Exception {
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        dto.setTitle("Mein Titel");
+        MockMultipartFile file = new MockMultipartFile("file", "scan.pdf", "application/pdf", new byte[]{1});
+        Document saved = Document.builder().id(UUID.randomUUID()).title("Mein Titel")
+                .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("path", "hash"));
+
+        ArgumentCaptor<Document> captor = ArgumentCaptor.forClass(Document.class);
+        documentService.createDocument(dto, file);
+
+        verify(documentRepository, atLeastOnce()).save(captor.capture());
+        assertThat(captor.getAllValues().get(0).getTitle()).isEqualTo("Mein Titel");
+    }
+
     // ─── createDocument metadataComplete ─────────────────────────────────────
 
     @Test