fix(deps): update dependency next to v15.4.7 [security]

Author: renovate[bot]

apps/next-app/package.json

@@ -13,7 +13,7 @@
     "@my-repo/transactional": "workspace:*",
     "@react-email/components": "^0.1.0",
     "@react-email/render": "1.1.3",
-    "next": "15.3.5",
+    "next": "15.4.7",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "resend": "^4.0.0"