- Add bookshelf route with library selection from query param or first available
- Add filter bar UI with library selector, search, and filter controls
- Integrate HTMX for dynamic filtering (hx-get to /api/media-items/filtered)
- Add Alpine.js component for filter state management
- Add filter save/load functionality via /api/bookshelf/filters endpoint
- Update bookshelf.ts to use Alpine.js for reactive state instead of DOM manipulation