fix: bump next version to fix new vulnerabilities

Author: KrzysztofSajko

src/frontend/package-lock.json

@@ -41,7 +41,7 @@
     "currency-symbol-map": "5.1.0",
     "dotenv": "17.2.3",
     "dotenv-expand": "12.0.3",
-    "next": "^15.5.7",
+    "next": "^15.5.9",
     "react": "^19.2.1",
     "react-dom": "^19.2.1",
     "sharp": "0.34.4",