feat(user): implement OTP login, user creation, and profile management

- Added SendOTP method for simulating OTP sending.
- Implemented LoginWithOTP method for user login/registration via OTP, including user creation if not found.
- Added Me method to retrieve current user information.
- Implemented Update method for updating user profile details.
- Added RealName method for real-name verification.
- Implemented GetNotifications method to fetch user notifications.
- Created user_test.go for comprehensive unit tests covering login, profile retrieval, updates, real-name verification, and notifications.
- Updated database models to use appropriate consts for fields like gender, status, and roles.

backend/app/services/content.go

@@ -61,4 +61,4 @@ func (s *content) RemoveLike(ctx context.Context, contentId string) error {
 
 func (s *content) ListTopics(ctx context.Context) ([]content_dto.Topic, error) {
 	return []content_dto.Topic{}, nil
-}
+}