- Add LoginScreen component with Gateway URL + Token fields
- Store credentials in localStorage (not in bundle)
- Auto-reconnect with stored credentials on reload
- Add logout button (LogOut icon) in Header
- Remove VITE_GATEWAY_TOKEN from .env.example
- VITE_GATEWAY_WS_URL now only pre-fills the URL field
- Dark neon theme consistent with rest of app
Closes feedback item #4
