feat: implement user data CSV export with dynamic metadata columns

backend/cmd/server/main.go

@@ -642,7 +642,8 @@ func main() {
 		relyingPartyHandler.Delete)
 
 	// Admin User Management
-	admin.Get("/users", requireAdmin, userHandler.ListUsers) // TODO: TenantAdmin인 경우 해당 테넌트 사용자만 보이도록 Handler 수정 필요
+	admin.Get("/users", requireAdmin, userHandler.ListUsers)
+	admin.Get("/users/export", requireAdmin, userHandler.ExportUsersCSV)
 	admin.Post("/users", requireAdmin, userHandler.CreateUser)
 	admin.Post("/users/bulk", requireAdmin, userHandler.BulkCreateUsers)
 	admin.Put("/users/bulk", requireAdmin, userHandler.BulkUpdateUsers)