fix(fc2a): apply ruff autofix + skip vue-tsc check (no tsconfig)

Ruff:
The remaining I001 errors came from ruff treating `alembic` as a first-
party module (because the alembic/ directory exists in the repo root)
rather than third-party. Ran `ruff check --fix` locally — auto-sorted
import groupings to put alembic/sqlalchemy alongside backend.* as first-
party, and trimmed redundant blank lines after a few import blocks.

Frontend:
`npm run check` (vue-tsc --noEmit) was failing because vue-tsc has no
tsconfig.json to read against, and the frontend is pure JS without
JSDoc annotations — vue-tsc had nothing to do. Skipping the step until
we add a tsconfig + convert to TS or add JSDoc annotations.

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

backend/app/tasks/maintenance.py

@@ -9,7 +9,6 @@ from ..celery_app import celery
 from ..config import get_config
 from ..models import ImportTask
 
-
 STUCK_THRESHOLD_MINUTES = 30
 OLD_TASK_DAYS = 7
 

backend/app/tasks/thumbnail.py

@@ -16,7 +16,6 @@ from ..models import ImageRecord
 from ..services.importer import is_video
 from ..services.thumbnailer import Thumbnailer
 
-
 IMAGES_ROOT = Path("/images")