build(deps): bump next from 13.5.6 to 15.1.5 in /client

Bumps [next](https://github.com/vercel/next.js) from 13.5.6 to 15.1.5.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v13.5.6...v15.1.5)

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

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

client/package.json

@@ -35,7 +35,7 @@
     "cmdk": "^1.0.0",
     "lucide-react": "^0.436.0",
     "markdown-to-jsx": "^7.4.1",
-    "next": "13.5.6",
+    "next": "15.1.5",
     "next-themes": "^0.3.0",
     "react": "^18",
     "react-dom": "^18",