fix(deps): update dependency better-auth to ~1.3.16

Author: renovate[bot]

packages/auth/package.json

@@ -31,7 +31,7 @@
     "@acme/db": "workspace:*",
     "@better-auth/stripe": "~1.3.14",
     "@t3-oss/env-nextjs": "~0.13.8",
-    "better-auth": "~1.3.9",
+    "better-auth": "~1.3.16",
     "zod": "~3.25.71"
   },
   "devDependencies": {