- Add backend/celery_app.py: Celery("docuvault") with Redis broker, JSON
serialization, and tasks.document_tasks.* routed to documents queue;
reads REDIS_URL directly from os.environ (no config import — Pitfall 7)
- Add backend/tasks/__init__.py: empty package marker
- Add backend/tasks/document_tasks.py: sync extract_and_classify Celery task
that calls asyncio.run(_run()) to retrieve bytes from MinIO, extract text
via extractor, and classify via classifier; classification failure is non-fatal
- Update backend/services/classifier.py: classify_document and
suggest_topics_for_document now accept session: AsyncSession as first arg;
all storage.* calls updated to async session-injection pattern
- Add extract_text_from_bytes helper to services/extractor.py for bytes-based
extraction (used by Celery worker, which retrieves bytes from MinIO)
curo1305