⬆️(dependencies) update next to v15.5.7 [SECURITY]

Author: renovate[bot]

src/frontend/package-lock.json

@@ -20,7 +20,7 @@
     "i18next-browser-languagedetector": "8.1.0",
     "react": "19.1.0",
     "react-dom": "19.1.0",
-    "next": "15.5.4",
+    "next": "15.5.7",
     "react-i18next": "15.4.1",
     "react-toastify": "11.0.2",
     "sass": "1.85.0"