Bump next from 15.2.1 to 15.4.8

Bumps [next](https://github.com/vercel/next.js) from 15.2.1 to 15.4.8.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.2.1...v15.4.8)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.4.8
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -14,7 +14,7 @@
     "@ai-sdk/openai": "^1.2.1",
     "@ai-sdk/react": "^1.1.21",
     "ai": "^4.1.53",
-    "next": "15.2.1",
+    "next": "15.4.8",
     "openai": "^5.1.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",