chore: upgrade nextjs

Author: tonylepmets

frontend/package.json

@@ -20,7 +20,7 @@
     "@vercel/speed-insights": "^1.2.0",
     "autoprefixer": "^10.4.21",
     "date-fns": "^4.1.0",
-    "next": "^15.5.0",
+    "next": "15.5.7",
     "next-sanity": "^10.0.14",
     "postcss": "^8.5.6",
     "react": "^19.1.1",