refactor(notification-outbox): clarify Health outbox-KPI seed value

src/ScadaLink.CentralUI/Components/Pages/Monitoring/Health.razor

@@ -332,7 +332,15 @@
 
     // Notification Outbox headline KPIs, refreshed alongside the site states.
     private NotificationKpiResponse _outboxKpi =
-        new(string.Empty, true, null, 0, 0, 0, 0, null);
+        new(
+            CorrelationId: string.Empty,
+            Success: false,
+            ErrorMessage: null,
+            QueueDepth: 0,
+            StuckCount: 0,
+            ParkedCount: 0,
+            DeliveredLastInterval: 0,
+            OldestPendingAge: null);
     private bool _outboxKpiAvailable;
     private string? _outboxKpiError;