Bump next from 15.5.6 to 15.5.7 (#113)

Bumps [next](https://github.com/vercel/next.js) from 15.5.6 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@v15.5.6...v15.5.7)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

frontend/package.json

@@ -2,7 +2,7 @@
   "dependencies": {
     "@aws-amplify/adapter-nextjs": "^1.6.9",
     "aws-amplify": "^6.15.6",
-    "next": "^15.3.2",
+    "next": "^15.5.7",
     "react": "19.2.0",
     "react-dom": "19.2.0"
   },