chore(deps): update dependency eslint-config-next to v15.5.9

Author: renovate[bot]

ui/package.json

@@ -34,7 +34,7 @@
     "@types/react": "^19.2.8",
     "@types/react-dom": "^19.2.3",
     "eslint": "^9.39.2",
-    "eslint-config-next": "16.1.4",
+    "eslint-config-next": "15.5.9",
     "patch-package": "^8.0.1",
     "postcss": "^8.5.6",
     "tailwindcss": "^4.1.18",