Remove unused shadcn components and react-highlight-words

Remove aspect-ratio, checkbox, command, input-group, kbd, and slider
components — none are imported anywhere. Remove react-highlight-words
npm package — replaced by custom implementation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ChristianChiarulli

app/package.json

@@ -49,7 +49,6 @@
     "lucide-react": "^0.577.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
-    "react-highlight-words": "^0.21.0",
     "react-intersection-observer": "^10.0.3",
     "shadcn": "^4.0.3",
     "sonner": "^2.0.7",