Add AI-suggested editable document title

AI now returns a short descriptive title per document (e.g. "ACME Corp
Invoice April 2026"). Title is stored in a new documents.title column
(migration 0002), shown in the row header instead of the raw filename,
and editable inline via PATCH /documents/{id}/title. Filename is shown
as a subtitle when a title exists.

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

features/doc-service/app/routers/documents.py

@@ -16,7 +16,7 @@ from app.deps import get_user_id
 from app.models.category import DocumentCategory
 from app.models.category_assignment import CategoryAssignment
 from app.models.document import Document
-from app.schemas.document import DocumentOut, DocumentStatusOut, DocumentTypeUpdate, TagsUpdate
+from app.schemas.document import DocumentOut, DocumentStatusOut, DocumentTypeUpdate, TagsUpdate, TitleUpdate
 from app.services.ai_client import AIServiceError, classify_document
 from app.services.config_reader import load_doc_config
 from app.services.storage import delete_file, get_upload_path, save_upload
@@ -95,6 +95,7 @@ async def process_document(doc_id: str) -> None:
 
             doc.raw_text = text[:500_000]  # cap stored text at 500k chars
             doc.extracted_data = json.dumps(result)
+            doc.title = result.get("title") or None
             doc.document_type = result.get("document_type", "unknown")
             doc.tags = json.dumps(result.get("tags", []))
             doc.status = "done"
@@ -227,6 +228,20 @@ async def update_document_tags(
     return _doc_with_categories(doc)
 
 
+@router.patch("/{doc_id}/title", response_model=DocumentOut)
+async def update_document_title(
+    doc_id: str,
+    body: TitleUpdate,
+    user_id: str = Depends(get_user_id),
+    db: AsyncSession = Depends(get_db),
+) -> DocumentOut:
+    doc = await _get_user_doc(doc_id, user_id, db)
+    doc.title = body.title.strip() or None
+    await db.commit()
+    doc = await _get_user_doc(doc_id, user_id, db)
+    return _doc_with_categories(doc)
+
+
 @router.delete("/{doc_id}", status_code=204)
 async def delete_document(
     doc_id: str,