Bump next from 14.2.35 to 15.5.21

Bumps [next](https://github.com/vercel/next.js) from 14.2.35 to 15.5.21.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Commits](https://github.com/vercel/next.js/compare/v14.2.35...v15.5.21)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.21
  dependency-type: direct:production
...

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

package.json

@@ -19,7 +19,7 @@
     "embla-carousel-react": "^8.1.5",
     "gh-pages": "^6.1.1",
     "lucide-react": "^0.395.0",
-    "next": "14.2.35",
+    "next": "15.5.21",
     "react": "^18",
     "react-dom": "^18",
     "tailwind-merge": "^2.3.0",