chore: add pre-commit ruff hook with auto-fix

- scripts/hooks/pre-commit: runs ruff --fix for root and web/ (matching CI)
  and re-stages any auto-fixed files so they land in the commit
- Makefile: add install-hooks target (run once after clone)
- pyproject.toml: exclude web/ from root ruff (web has its own config)
- Fix remaining import sort warnings caught by the new hook

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/tests/test_billing_routes.py

@@ -144,9 +144,8 @@ class TestCancelRoute:
 # subscription_required decorator
 # ════════════════════════════════════════════════════════════
 
-from quart import Blueprint  # noqa: E402
-
 from beanflows.auth.routes import subscription_required  # noqa: E402
+from quart import Blueprint  # noqa: E402
 
 test_bp = Blueprint("test", __name__)