Update the /admin/library route handler to fetch and pass data to
template for server-side rendering, improving page load performance.
Changes:
- Fetch all libraries using ListLibrariesData() helper
- Fetch all users for visibility management
- Convert database rows to template types (LibraryData, User)
- Pass data to AdminLibrary template for SSR
- Follows existing pattern from dashboard and custom-section pages
Benefits:
- Faster initial page load (no AJAX fetch)
- Better UX (content visible immediately)
- Progressive enhancement (works without JS)