fix(deps): update nextjs monorepo to v15.5.15 (#253)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

bun.lock

@@ -11,7 +11,7 @@
   "dependencies": {
     "bootstrap-italia": "2.18.0",
     "design-react-kit": "5.8.3",
-    "next": "15.5.14",
+    "next": "15.5.15",
     "react": "19.2.4",
     "react-dom": "19.2.4",
     "typeface-lora": "1.1.13",
@@ -24,7 +24,7 @@
     "@types/react": "19.2.14",
     "@types/react-dom": "19.2.3",
     "eslint": "9.39.4",
-    "eslint-config-next": "15.5.14",
+    "eslint-config-next": "15.5.15",
     "typescript": "5.9.3"
   }
 }