Backend Check

Steps

1. Format: poetry run format — runs formatting AND linting. NEVER run ruff/black/isort individually
2. Fix any remaining errors manually, re-run until clean
3. Test: poetry run test (runs DB setup + pytest). For specific files: poetry run pytest -s -vvv <test_files>
4. Snapshots (if needed): poetry run pytest path/to/test.py --snapshot-update — review with git diff