Merge branch 'feature/user-group' into dev

backend/internal/repository/user_group_repository.go

@@ -37,7 +37,8 @@ func (r *userGroupRepository) Delete(ctx context.Context, id string) error {
 
 func (r *userGroupRepository) FindByID(ctx context.Context, id string) (*domain.UserGroup, error) {
 	var group domain.UserGroup
-	if err := r.db.WithContext(ctx).First(&group, "id = ?", id).Error; err != nil {
+	// Using Where to be more explicit and avoid issues with GORM's default primary key handling if ID is string/uuid
+	if err := r.db.WithContext(ctx).Where("id = ?", id).First(&group).Error; err != nil {
 		return nil, err
 	}
 	return &group, nil