Complete UI redesign with sidebar navigation and card-based layout

- Added sidebar navigation with collapsible menu
- Implemented card-based dashboard layout similar to modern dashboards
- Created separate views: Dashboard, Scans, Notifications, Activities
- Dashboard view shows status cards and quick actions in grid layout
- Scans view shows detailed pending scans list
- Activities view shows all Plex activities
- Notifications view with search and filtering
- Modern, clean design with better visual hierarchy
- Responsive design for mobile devices
- Removed AI-generated look for more professional appearance

Author: devinvee