feat(user): add user creation endpoint for superusers

- Add new `/userMgr/create` endpoint for superusers to create users with specified types
- Update AddUser function to accept user type parameter
- Add documentation for the new endpoint in api.md
- Remove debug log comment in auth.go

router.go

@@ -12,6 +12,8 @@ func setupRoutes() {
 	http.HandleFunc("/login", LoginHandler)
 	http.HandleFunc("/logout", LogoutHandler)
 
+	http.HandleFunc("/userMgr/create", CreateUserHandler)
+
 	http.HandleFunc("/frpcAct/instanceMgr/create", CreateInstanceHandler)
 	http.HandleFunc("/frpcAct/instanceMgr/list", ListInstancesHandler)