Merge upstream/main into pr/upstream-model-tracking

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/internal/service/dashboard_service.go

@@ -169,6 +169,15 @@ func (s *DashboardService) GetGroupStatsWithFilters(ctx context.Context, startTi
 	return stats, nil
 }
 
+// GetGroupUsageSummary returns today's and cumulative cost for all groups.
+func (s *DashboardService) GetGroupUsageSummary(ctx context.Context, todayStart time.Time) ([]usagestats.GroupUsageSummary, error) {
+	results, err := s.usageRepo.GetAllGroupUsageSummary(ctx, todayStart)
+	if err != nil {
+		return nil, fmt.Errorf("get group usage summary: %w", err)
+	}
+	return results, nil
+}
+
 func (s *DashboardService) getCachedDashboardStats(ctx context.Context) (*usagestats.DashboardStats, bool, error) {
 	data, err := s.cache.GetDashboardStats(ctx)
 	if err != nil {