feat: upgrade next-auth to v5.0.0-beta.29 and refactor authentication middleware

- Updated next-auth dependency in package.json to version 5.0.0-beta.29.
- Refactored create-admin script to use a valid email format.
- Implemented authentication middleware for various API routes to enforce access control.
- Refactored API route handlers to improve readability and maintainability.
- Enhanced error handling in authentication error page.
- Added detailed tests for authentication flow, including protected routes and NextAuth endpoints.

src/app/api/auth/[...nextauth]/route.js

@@ -1,4 +1,3 @@
-import NextAuth from "@/lib/auth"
+import { handlers } from "@/lib/auth"
 
-export const GET = NextAuth
-export const POST = NextAuth
+export const { GET, POST } = handlers