chore(deps): bump next from 15.4.10 to 16.1.5 in /playground/nextjs

Bumps [next](https://github.com/vercel/next.js) from 15.4.10 to 16.1.5.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.4.10...v16.1.5)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 16.1.5
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

playground/nextjs/package.json

@@ -19,7 +19,7 @@
     "class-variance-authority": "^0.7.0",
     "clsx": "^2.1.1",
     "lucide-react": "^0.439.0",
-    "next": "15.4.10",
+    "next": "16.1.5",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-icons": "^5.0.1",