feat(upload): add POST /api/documents/quick-upload endpoint for bulk file upload

Adds a new multipart endpoint that accepts multiple files and creates one
document per file without requiring any form metadata. Each document gets
title = filename-without-extension and status = UPLOADED.

- Fix storeDocument() to strip the file extension from the document title
- Validate content type (PDF/JPEG/PNG/TIFF) server-side; unsupported files
  are skipped and returned as per-file errors in QuickUploadResult
- Tests cover 401/403 auth, success path, and unsupported file type

Closes #66 (backend part)

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

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

@@ -23,6 +23,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.UUID;
 
+import static org.hamcrest.Matchers.containsString;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.when;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@@ -121,6 +122,50 @@ class DocumentControllerTest {
                 .andExpect(status().isOk());
     }
 
+    // ─── POST /api/documents/quick-upload ────────────────────────────────────
+
+    @Test
+    void quickUpload_returns401_whenUnauthenticated() throws Exception {
+        mockMvc.perform(multipart("/api/documents/quick-upload"))
+                .andExpect(status().isUnauthorized());
+    }
+
+    @Test
+    @WithMockUser
+    void quickUpload_returns403_whenMissingWritePermission() throws Exception {
+        mockMvc.perform(multipart("/api/documents/quick-upload"))
+                .andExpect(status().isForbidden());
+    }
+
+    @Test
+    @WithMockUser(authorities = "WRITE_ALL")
+    void quickUpload_returns200_withValidPdfFile() throws Exception {
+        Document doc = Document.builder()
+                .id(UUID.randomUUID()).title("scan001").originalFilename("scan001.pdf").build();
+        when(documentService.storeDocument(any())).thenReturn(doc);
+
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("files", "scan001.pdf", "application/pdf", new byte[]{1});
+
+        mockMvc.perform(multipart("/api/documents/quick-upload").file(file))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.created[0].title").value("scan001"))
+                .andExpect(jsonPath("$.errors").isEmpty());
+    }
+
+    @Test
+    @WithMockUser(authorities = "WRITE_ALL")
+    void quickUpload_skipsUnsupportedFileType_andReturnsError() throws Exception {
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("files", "report.docx",
+                        "application/vnd.openxmlformats-officedocument.wordprocessingml.document", new byte[]{1});
+
+        mockMvc.perform(multipart("/api/documents/quick-upload").file(file))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.created").isEmpty())
+                .andExpect(jsonPath("$.errors[0]").value(containsString("report.docx")));
+    }
+
     // ─── GET /api/documents/{id}/versions ────────────────────────────────────
 
     @Test

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

@@ -212,6 +212,44 @@ class DocumentServiceTest {
         verify(documentVersionService).recordVersion(any(Document.class));
     }
 
+    // ─── storeDocument ───────────────────────────────────────────────────────
+
+    @Test
+    void storeDocument_setsTitle_withoutFileExtension_forNewDocument() throws Exception {
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("file", "scan001.pdf", "application/pdf", new byte[]{1});
+        FileService.UploadResult uploadResult = new FileService.UploadResult("documents/uuid_scan001.pdf", "abc123");
+        Document saved = Document.builder().id(UUID.randomUUID()).title("scan001").originalFilename("scan001.pdf").build();
+
+        when(documentRepository.findByOriginalFilename("scan001.pdf")).thenReturn(Optional.empty());
+        when(documentRepository.save(any())).thenReturn(saved);
+        when(fileService.uploadFile(any(), any())).thenReturn(uploadResult);
+
+        org.mockito.ArgumentCaptor<Document> captor = org.mockito.ArgumentCaptor.forClass(Document.class);
+        documentService.storeDocument(file);
+
+        verify(documentRepository).save(captor.capture());
+        assertThat(captor.getValue().getTitle()).isEqualTo("scan001");
+    }
+
+    @Test
+    void storeDocument_preservesExistingTitle_whenPlaceholderAlreadyExists() throws Exception {
+        org.springframework.mock.web.MockMultipartFile file =
+                new org.springframework.mock.web.MockMultipartFile("file", "scan001.pdf", "application/pdf", new byte[]{1});
+        FileService.UploadResult uploadResult = new FileService.UploadResult("documents/uuid_scan001.pdf", "abc123");
+        Document placeholder = Document.builder()
+                .id(UUID.randomUUID()).title("Brief an Oma").originalFilename("scan001.pdf")
+                .status(org.raddatz.familienarchiv.model.DocumentStatus.PLACEHOLDER).build();
+
+        when(documentRepository.findByOriginalFilename("scan001.pdf")).thenReturn(Optional.of(placeholder));
+        when(documentRepository.save(any())).thenReturn(placeholder);
+        when(fileService.uploadFile(any(), any())).thenReturn(uploadResult);
+
+        documentService.storeDocument(file);
+
+        assertThat(placeholder.getTitle()).isEqualTo("Brief an Oma");
+    }
+
     // ─── backfillFileHashes ───────────────────────────────────────────────────
 
     @Test