feat(platform): add online statistics summary

vehicle-data-platform/apps/api/internal/platform/service.go

@@ -871,6 +871,44 @@ func (s *Service) DailyMileage(ctx context.Context, query url.Values) (Page[Dail
 	return s.store.DailyMileage(ctx, resolvedQuery)
 }
 
+func (s *Service) OnlineStatisticsSummary(ctx context.Context, query url.Values) (OnlineStatisticsSummary, error) {
+	resolvedQuery, err := s.resolveVehicleQuery(ctx, query)
+	if err != nil {
+		return OnlineStatisticsSummary{}, err
+	}
+	coverage, err := s.store.VehicleCoverageSummary(ctx, resolvedQuery)
+	if err != nil {
+		return OnlineStatisticsSummary{}, err
+	}
+	serviceSummary, err := s.store.VehicleServiceSummary(ctx)
+	if err != nil {
+		return OnlineStatisticsSummary{}, err
+	}
+	opsHealth, err := s.store.OpsHealth(ctx)
+	if err != nil {
+		return OnlineStatisticsSummary{}, err
+	}
+	total := coverage.TotalVehicles
+	online := coverage.OnlineVehicles
+	offline := total - online
+	if offline < 0 {
+		offline = 0
+	}
+	rate := 0.0
+	if total > 0 {
+		rate = float64(online) / float64(total) * 100
+	}
+	return OnlineStatisticsSummary{
+		VehicleCount:        total,
+		OnlineVehicleCount:  online,
+		OfflineVehicleCount: offline,
+		OnlineRatePercent:   rate,
+		RedisOnlineKeys:     opsHealth.RedisOnlineKeys,
+		ProtocolStats:       serviceSummary.Protocols,
+		Evidence:            "由车辆服务覆盖汇总、实时来源状态和 Redis 在线 key 计算",
+	}, nil
+}
+
 func (s *Service) QualitySummary(ctx context.Context, query url.Values) (QualitySummary, error) {
 	return s.store.QualitySummary(ctx, query)
 }