Add migration version check before running alembic upgrade to prevent
multiple uvicorn workers from running migrations simultaneously.
- Check current vs head revision before running migrations
- Skip migration if already at latest version
- Log current and head revision for debugging
- Add theme support with dark/light/system modes
- Add useTheme hook for applying user config theme
- Update router to use SettingsPage
- Update app-shell to apply theme on load
- Add CSS variables for dark theme
- Fix mypy errors in user_config.py
- Quality gates pass: ruff, mypy, typecheck, lint, build