chore(deps): bump next from 15.1.6 to 15.3.0 in /frontend

Bumps [next](https://github.com/vercel/next.js) from 15.1.6 to 15.3.0.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.1.6...v15.3.0)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

frontend/examples/nextjs/package.json

@@ -7,7 +7,7 @@
   },
   "dependencies": {
     "@teamhanko/hanko-elements": "^1.5.2",
-    "next": "^15.1.6",
+    "next": "^15.3.0",
     "react": "^18.2.0",
     "react-dom": "^18.2.0"
   },