Add re-analyse button and POST /documents/{id}/reprocess endpoint

Resets status to pending, clears error_message, and re-enqueues the
background AI extraction task. Button is disabled while the document
is already pending or processing; returns 409 in that case from the API.

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

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

@@ -305,6 +305,24 @@ async def update_document_title(
     return _doc_with_categories(doc)
 
 
+@router.post("/{doc_id}/reprocess", response_model=DocumentOut)
+async def reprocess_document(
+    doc_id: str,
+    background_tasks: BackgroundTasks,
+    user_id: str = Depends(get_user_id),
+    db: AsyncSession = Depends(get_db),
+) -> DocumentOut:
+    doc = await _get_user_doc(doc_id, user_id, db)
+    if doc.status in ("pending", "processing"):
+        raise HTTPException(status_code=409, detail="Document is already being processed")
+    doc.status = "pending"
+    doc.error_message = None
+    await db.commit()
+    background_tasks.add_task(process_document, doc_id)
+    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,