feat(platform): summarize missing vehicle sources

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

@@ -384,6 +384,24 @@ func TestHandlerVehicleServiceSummaryEndpoint(t *testing.T) {
 	if !noDataStatusFound {
 		t.Fatalf("summary service status distribution should include no_data, got %+v", body.Data.ServiceStatuses)
 	}
+	var rawBody struct {
+		Data struct {
+			MissingSources []struct {
+				Protocol string `json:"protocol"`
+				Count    int    `json:"count"`
+			} `json:"missingSources"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &rawBody); err != nil {
+		t.Fatalf("response JSON should decode raw summary: %v body=%s", err, rec.Body.String())
+	}
+	missing := map[string]int{}
+	for _, source := range rawBody.Data.MissingSources {
+		missing[source.Protocol] = source.Count
+	}
+	if missing["GB32960"] != 2 || missing["JT808"] != 2 || missing["YUTONG_MQTT"] != 3 {
+		t.Fatalf("summary should expose canonical missing source counts, got %+v body=%s", missing, rec.Body.String())
+	}
 }
 
 func TestHandlerVehicleServiceOverviewsEndpoint(t *testing.T) {