chore: Update auth files for NextAuth v5 compatibility

Breaking changes for NextAuth v5:
- Updated route.ts to use NextAuthConfig and new export pattern
- Changed getServerSession import to use auth from config
- Updated types and session handling for NextAuth v5
- Maintained backward compatibility with existing auth flow

frontend/app/api/auth/[...nextauth]/route.ts

@@ -2,8 +2,9 @@ import NextAuth from 'next-auth'
 import GitHub from 'next-auth/providers/github'
 import Google from 'next-auth/providers/google'
 import Credentials from 'next-auth/providers/credentials'
+import type { NextAuthConfig } from 'next-auth'
 
-const handler = NextAuth({
+export const config: NextAuthConfig = {
   providers: [
     GitHub({
       clientId: process.env.GITHUB_ID,
@@ -49,8 +50,8 @@ const handler = NextAuth({
     },
     async session({ session, token }) {
       if (session.user) {
-        session.user.id = token.id
-        session.user.email = token.email
+        session.user.id = token.id as string
+        session.user.email = token.email as string
       }
       return session
     }
@@ -59,6 +60,8 @@ const handler = NextAuth({
     strategy: 'jwt',
     maxAge: 30 * 24 * 60 * 60, // 30 days
   }
-})
+}
 
-export { handler as GET, handler as POST }
+export const { handlers, auth, signIn, signOut } = NextAuth(config)
+
+export { handlers as GET, handlers as POST }

frontend/lib/auth.ts

@@ -1,8 +1,8 @@
-import { getServerSession } from 'next-auth'
+import { auth } from '@/app/api/auth/[...nextauth]/route'
 import { redirect } from 'next/navigation'
 
 export async function requireAuth() {
-  const session = await getServerSession()
+  const session = await auth()
 
   if (!session || !session.user) {
     redirect('/auth/signin')