feat(api): add dashboard summary and system realtime endpoints

Add new admin API endpoints for dashboard metrics and system-wide
realtime statistics:

- Add /admin/dashboard/summary endpoint with aggregated metrics
  including requests, tokens, latency, masters, keys, and provider
  keys statistics with time period filtering
- Add /admin/realtime endpoint for system-level realtime stats
  aggregated across all masters
- Add status filter parameter to ListAPIKeys endpoint
- Add hour grouping option to log stats aggregation
- Update OpenAPI documentation with new endpoints and schemas

internal/service/stats.go

@@ -153,3 +153,69 @@ func readCmdTime(cmd *redis.StringCmd) *time.Time {
 	tm := time.Unix(v, 0).UTC()
 	return &tm
 }
+
+// SystemRealtimeSnapshot contains aggregated realtime stats across all masters
+type SystemRealtimeSnapshot struct {
+	TotalQPS         int64                   `json:"qps"`
+	TotalRPM         int64                   `json:"rpm"`
+	RateLimitedCount int64                   `json:"rate_limited_count"`
+	ByMaster         []MasterRealtimeSummary `json:"by_master"`
+	UpdatedAt        *time.Time              `json:"updated_at,omitempty"`
+}
+
+// MasterRealtimeSummary is a brief summary of a master's realtime stats
+type MasterRealtimeSummary struct {
+	MasterID    uint  `json:"master_id"`
+	QPS         int64 `json:"qps"`
+	RateLimited bool  `json:"rate_limited"`
+}
+
+// GetSystemRealtimeSnapshot aggregates realtime stats across all masters
+func (s *StatsService) GetSystemRealtimeSnapshot(ctx context.Context, masterIDs []uint) (SystemRealtimeSnapshot, error) {
+	if s == nil || s.rdb == nil {
+		return SystemRealtimeSnapshot{}, fmt.Errorf("redis client is required")
+	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
+
+	var totalQPS int64
+	var rateLimitedCount int64
+	byMaster := make([]MasterRealtimeSummary, 0, len(masterIDs))
+	var latestUpdatedAt *time.Time
+
+	for _, masterID := range masterIDs {
+		snapshot, err := s.GetMasterRealtimeSnapshot(ctx, masterID)
+		if err != nil {
+			continue // Skip masters with errors
+		}
+
+		totalQPS += snapshot.QPS
+		if snapshot.RateLimited {
+			rateLimitedCount++
+		}
+
+		byMaster = append(byMaster, MasterRealtimeSummary{
+			MasterID:    masterID,
+			QPS:         snapshot.QPS,
+			RateLimited: snapshot.RateLimited,
+		})
+
+		if snapshot.UpdatedAt != nil {
+			if latestUpdatedAt == nil || snapshot.UpdatedAt.After(*latestUpdatedAt) {
+				latestUpdatedAt = snapshot.UpdatedAt
+			}
+		}
+	}
+
+	// Estimate RPM as QPS * 60 (since we're measuring requests per second)
+	totalRPM := totalQPS * 60
+
+	return SystemRealtimeSnapshot{
+		TotalQPS:         totalQPS,
+		TotalRPM:         totalRPM,
+		RateLimitedCount: rateLimitedCount,
+		ByMaster:         byMaster,
+		UpdatedAt:        latestUpdatedAt,
+	}, nil
+}