build(deps): bump next in the npm_and_yarn group across 1 directory

Bumps the npm_and_yarn group with 1 update in the / directory: [next](https://github.com/vercel/next.js).


Updates `next` from 15.5.15 to 15.5.18
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.5.15...v15.5.18)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.18
  dependency-type: direct:production
  dependency-group: npm_and_yarn
...

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

Author: dependabot[bot]

package.json

@@ -21,7 +21,7 @@
     "ai": "^6.0.158",
     "clsx": "^2.1.1",
     "lucide-react": "^0.468.0",
-    "next": "^15.3.0",
+    "next": "^15.5.18",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "react-markdown": "^9.0.3",