UID2-6731: Update flatted to 3.4.0 to fix CVE-2026-32141

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: swibi-ttd

web-integrations/google-secure-signals/react-client-side/package-lock.json

@@ -10,6 +10,7 @@
     "dotenv": "^16.0.0",
     "ejs": "^3.1.9",
     "express": "^4.18.0",
+    "flatted": "^3.4.0",
     "nth-check": "^2.0.1",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",