fix(deps): update dependency firebase-admin to v13

Author: renovate[bot]

functions/package.json

@@ -17,7 +17,7 @@
     "@google-cloud/firestore": "^7.11.6",
     "axios": "^1.13.2",
     "express": "^4.22.0",
-    "firebase-admin": "^11.11.1",
+    "firebase-admin": "^13.6.1",
     "firebase-functions": "^4.9.0"
   },
   "private": true