- Convert admin dashboard from single 2-column page to multi-page interface
- Create main admin dashboard (/admin) as overview with navigation sidebar
- Add separate profile settings page (/admin/profile) for user account management
- Add separate library management page (/admin/library) combining folder and scan settings
- Implement sidebar navigation pattern similar to Gitea, Jellyfin, Audiobookshelf
- Add dedicated templates: admin.html, admin_profile.html, admin_library.html
- Include quick actions and statistics on main dashboard
- Improve UI with better organization and visual hierarchy
- Maintain consistent navigation and theme across all admin pages
- Add folder management, scan settings, and library statistics to library page
