fix: revert tab name and improve group list error handling

adminfront/src/locales/en.toml

@@ -807,7 +807,7 @@ header_subtitle = "Update tenant information or manage integration settings."
 loading = "Loading tenant information..."
 tab_admins = "Admin Settings"
 tab_federation = "External Integration"
-tab_organization = "Organization"
+tab_organization = "Sub-tenant Management"
 tab_profile = "Profile"
 tab_schema = "User Schema"
 title = "Tenant Details"

adminfront/src/locales/ko.toml

@@ -811,7 +811,7 @@ header_subtitle = "테넌트 정보를 수정하거나 연동 설정을 관리
 loading = "테넌트 정보를 불러오는 중..."
 tab_admins = "관리자 설정"
 tab_federation = "외부 연동"
-tab_organization = "조직 관리"
+tab_organization = "하위 테넌트 관리"
 tab_profile = "프로필"
 tab_schema = "사용자 스키마"
 title = "테넌트 상세"

backend/internal/service/user_group_service.go

@@ -192,12 +192,19 @@ func (s *userGroupService) List(ctx context.Context, tenantID string) ([]domain.
 		return nil, err
 	}
 
+	if s.ketoService == nil {
+		return groups, nil
+	}
+
 	// For each group, fetch member count from Keto
 	for i := range groups {
 		tuples, err := s.ketoService.ListRelations(ctx, "Tenant", groups[i].ID, "members", "")
 		if err == nil {
 			// Create dummy members just to carry the count for the JSON response
 			groups[i].Members = make([]domain.User, len(tuples))
+		} else {
+			slog.Warn("Failed to fetch member count from Keto", "groupID", groups[i].ID, "error", err)
+			groups[i].Members = []domain.User{}
 		}
 	}