Bump next from 15.5.19 to 16.2.9 in /frontend

Bumps [next](https://github.com/vercel/next.js) from 15.5.19 to 16.2.9.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.5.19...v16.2.9)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 16.2.9
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

frontend/package-lock.json

@@ -28,7 +28,7 @@
     "date-fns": "^4.4.0",
     "html2canvas": "^1.4.1",
     "lucide-react": "^1.21.0",
-    "next": "15.5.19",
+    "next": "16.2.9",
     "next-themes": "^0.4.6",
     "patch-package": "^8.0.1",
     "prettier": "^3.8.4",