add tagging system for media items

Introduces user-defined tag categories and tags with a many-to-many
relationship to media items. Tags are stored in a SQLite database
(medialore.db via better-sqlite3) with ON DELETE CASCADE for automatic
cleanup. Users can manage categories and tags at /manage/tags, assign
tags to games in the detail modal, and tag mixed media files via a
hover button on each tile.

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

src/components/games/GameDetailModal.tsx

@@ -2,6 +2,7 @@
 
 import { useEffect, useRef } from 'react'
 import type { Game } from '@/types'
+import TagSelector from '@/components/tags/TagSelector'
 
 interface Props {
   game: Game
@@ -90,6 +91,14 @@ export default function GameDetailModal({ game, libraryId, onClose }: Props) {
             <span>↓</span>
             Download .zip
           </a>
+
+          {/* Tags */}
+          <div className="mt-4 pt-4" style={{ borderTop: '1px solid var(--border)' }}>
+            <p className="text-xs font-semibold uppercase tracking-wider mb-2" style={{ color: 'var(--text-secondary)' }}>
+              Tags
+            </p>
+            <TagSelector mediaKey={`${libraryId}:${game.id}`} />
+          </div>
         </div>
       </div>
     </div>