fix(workers): worker-level recovery — autoretry on transient errors + tightened sweep (5min) + import_media_file body-wrap so no path leaves rows stuck in 'processing'

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/tasks/thumbnail.py

@@ -7,6 +7,8 @@ so they deserve their own queue lane.
 
 from pathlib import Path
 
+from sqlalchemy.exc import DBAPIError, OperationalError
+
 from ..celery_app import celery
 from ..models import ImageRecord
 from ..services.importer import is_video
@@ -16,7 +18,17 @@ from ._sync_engine import sync_session_factory as _sync_session_factory
 IMAGES_ROOT = Path("/images")
 
 
-@celery.task(name="backend.app.tasks.thumbnail.generate_thumbnail", bind=True)
+@celery.task(
+    name="backend.app.tasks.thumbnail.generate_thumbnail",
+    bind=True,
+    autoretry_for=(OperationalError, DBAPIError, OSError),
+    retry_backoff=5,
+    retry_backoff_max=60,
+    retry_jitter=True,
+    max_retries=3,
+    soft_time_limit=120,
+    time_limit=180,
+)
 def generate_thumbnail(self, image_id: int) -> dict:
     SessionLocal = _sync_session_factory()
     with SessionLocal() as session: