feat: Add GitHub Actions CI for PR protection

- Add CI workflow with Python (ruff lint, security tests) and UI (ESLint, TypeScript, build) jobs
- Add ruff, mypy, pytest to requirements.txt
- Add pyproject.toml with ruff configuration
- Fix import sorting across Python files (ruff --fix)
- Fix test_security.py expectations to match actual security policy
- Remove invalid 'eof' command from ALLOWED_COMMANDS

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

start_ui.py

@@ -28,7 +28,6 @@ import time
 import webbrowser
 from pathlib import Path
 
-
 ROOT = Path(__file__).parent.absolute()
 VENV_DIR = ROOT / "venv"
 UI_DIR = ROOT / "ui"
@@ -158,9 +157,9 @@ def start_dev_server(port: int) -> tuple:
     """Start both Vite and FastAPI in development mode."""
     venv_python = get_venv_python()
 
-    print(f"\n  Starting development servers...")
+    print("\n  Starting development servers...")
     print(f"  - FastAPI backend: http://127.0.0.1:{port}")
-    print(f"  - Vite frontend:   http://127.0.0.1:5173")
+    print("  - Vite frontend:   http://127.0.0.1:5173")
 
     # Start FastAPI
     backend = subprocess.Popen([