build(deps): bump next from 15.5.9 to 16.1.5

Bumps [next](https://github.com/vercel/next.js) from 15.5.9 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](https://github.com/vercel/next.js/compare/v15.5.9...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>

package.json

@@ -13,7 +13,7 @@
     "@vercel/speed-insights": "^1.2.0",
     "axios": "^1.12.0",
     "date-fns": "^4.1.0",
-    "next": "15.5.9",
+    "next": "16.1.5",
     "react": "^19.0.0",
     "react-datepicker": "^8.4.0",
     "react-dom": "^19.0.0"