fix: only allow pnpm as package manager

package.json

@@ -6,6 +6,7 @@
     "seed": "ts-node --compiler-options {\"module\":\"CommonJS\"} prisma/seed.ts"
   },
   "scripts": {
+    "preinstall": "npx only-allow pnpm",
     "postinstall": "prisma generate",
     "dev": "next dev",
     "build": "next build",