1.6.5

feat: implement dark theme and enhance UI components

- Updated AppContext to default to dark theme.
- Enhanced CSS variables for light and dark themes, including semantic colors for backgrounds, text, and borders.
- Refactored SettingsPage to include system behavior options (run on startup, run in background, system notifications).
- Updated various pages (Login, Register, Forgot Password, etc.) to use theme-aware background colors and input styles.
- Added tray icon for application.
- Improved accessibility and visual consistency across components with updated styles.