IAV-918: Add notification system with drawer and configuration page
Summary
- Add a notification drawer accessible via the bell icon in the dashboard header, with real-time filtering (all, unread, read, favorites) search, and per-notification actions (favorite, mark read/unread, archive, delete)
- Add a dedicated notifications page (
/dashboard/notifications) with two tabs: Configuration (channels, types, frequency, silence hours) and Archives (with category and agent sub-filters) - Introduce notification types, mock data, and reusable components with glassmorphism design