fix: pause usage polling on auth errors
- Show the same auth warning state for expired, invalid, or missing credentials
- Replace the widget auth text with a warning symbol and updated the toast notification
- Stop usage polling and countdown timers while auth is required
- Reuse the configured poll interval to watch credential file metadata instead of polling the API
- Auto-recover when credentials change, while still supporting manual refresh and restart flows
Updated translations
- Added a native system tray icon that shows current 5-hour usage as a percentage badge.
- Added tray icon tooltip support showing both 5h and 7d countdown/usage values.
- Added tray icon interactions: left-click toggles the taskbar widget, right-click opens the context menu.
- Anchored widget to the bottom of the taskbar
- Added embedded app icon loading so tray fallback uses the app's own icon.
- Updated countdown timer logic to stop cases where 61m is shown
- Updated README.md
