- Added theme state management (light/dark/system)
- Implemented OS theme detection and automatic sync
- Added theme toggle UI in sidebar with 3 buttons
- Applied dark mode styles to all components:
- Sidebar with dark backgrounds and borders
- Note editor with dark text and inputs
- Toolbar buttons with dark hover states
- TipTap editor with dark mode text and code blocks
- Theme preference saved to localStorage
- Enabled Tailwind dark mode with class strategy
- Smooth transitions between themes
- Added logout button at bottom of sidebar
- Display username with avatar (first letter)
- Clear all credentials and state on logout
- Username persists from saved credentials
- Clean logout flow returns to login screen
