Bump next from 15.5.2 to 15.5.7 in /webapp

Bumps [next](https://github.com/vercel/next.js) from 15.5.2 to 15.5.7.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.5.2...v15.5.7)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.7
  dependency-type: direct:production
...

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

Author: dependabot[bot]

webapp/package-lock.json

@@ -21,7 +21,7 @@
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "lucide-react": "^0.488.0",
-    "next": "15.5.2",
+    "next": "15.5.7",
     "next-safe-action": "^7.10.5",
     "next-themes": "^0.4.6",
     "prisma": "^6.6.0",