feat(platform): add filtered vehicle coverage summary

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

@@ -63,6 +63,14 @@ type VehicleCoverageRow struct {
 	ServiceStatus     *VehicleServiceStatus `json:"serviceStatus,omitempty"`
 }
 
+type VehicleCoverageSummary struct {
+	TotalVehicles       int `json:"totalVehicles"`
+	OnlineVehicles      int `json:"onlineVehicles"`
+	SingleSourceVehicles int `json:"singleSourceVehicles"`
+	MultiSourceVehicles  int `json:"multiSourceVehicles"`
+	UnboundVehicles      int `json:"unboundVehicles"`
+}
+
 type VehicleIdentityResolution struct {
 	LookupKey     string                `json:"lookupKey"`
 	Resolved      bool                  `json:"resolved"`