Strip template artifacts and fix lint errors

Remove npm lockfile, unused create-next-app SVGs, project-specific
next.config workarounds, and the unused @remixicon/react and date-fns deps.

Replace three set-state-in-effect patterns with useSyncExternalStore in
use-mobile, DialogPortal, and Carousel; the carousel change also fixes a
leaked reInit listener. yarn lint and yarn build are clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K8PmydbW6A1S2Tw3SFc3Cg

package.json

@@ -11,12 +11,10 @@
   "dependencies": {
     "@base-ui/react": "^1.6.0",
     "@next/swc-wasm-web": "16.2.10",
-    "@remixicon/react": "^4.9.0",
     "@shadcn/react": "^0.1.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "cmdk": "^1.1.1",
-    "date-fns": "^4.4.0",
     "embla-carousel-react": "^8.6.0",
     "input-otp": "^1.4.2",
     "lucide-react": "^1.22.0",