add library filter panel and tag selector enhancements

- Add left sidebar filter panel to MixedView and GamesView with name
  search and tag toggles; only shows tags/categories used in the current
  library; AND logic when multiple tags are selected
- Add GET /api/tags/library-assignments endpoint returning all tag
  assignments for a library keyed by mediaKey
- Add getTagAssignmentsForLibrary() and getTagsSortedByUsage() to tags lib
- Support ?sort=usage on GET /api/tags/items to order by assignment count
- Tag selector: per-category search, top-25-by-usage display, inline add
  tag (auto-assigned to current item) and add category flows
- Tag selector: group assigned tags by category into nested pills
- Fix nested <button> hydration error in EntryTile (outer element is now
  a div with role="button")
- Keep filter panel assignments in sync when tags are toggled or created

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/games/GameDetailModal.tsx

@@ -8,9 +8,10 @@ interface Props {
   game: Game
   libraryId: string
   onClose: () => void
+  onTagsChanged?: () => void
 }
 
-export default function GameDetailModal({ game, libraryId, onClose }: Props) {
+export default function GameDetailModal({ game, libraryId, onClose, onTagsChanged }: Props) {
   const overlayRef = useRef<HTMLDivElement>(null)
 
   useEffect(() => {
@@ -97,7 +98,7 @@ export default function GameDetailModal({ game, libraryId, onClose }: Props) {
             <p className="text-xs font-semibold uppercase tracking-wider mb-2" style={{ color: 'var(--text-secondary)' }}>
               Tags
             </p>
-            <TagSelector mediaKey={`${libraryId}:${game.id}`} />
+            <TagSelector mediaKey={`${libraryId}:${game.id}`} onTagsChanged={onTagsChanged} />
           </div>
         </div>
       </div>