Fix zod version: v4 doesn't exist, use v3.23.8

Author: eldinmiller

api/package.json

@@ -19,7 +19,7 @@
     "fastify": "^5.2.1",
     "fastify-plugin": "^5.1.0",
     "pino-pretty": "^13.0.0",
-    "zod": "^4.3.5"
+    "zod": "^3.23.8"
   },
   "devDependencies": {
     "@types/node": "^22.10.2",