feat(audit): M5.2 per-node stuck-count KPIs (T6) — repo per-node aggregation, actor message pair, CentralUI tiles

src/ZB.MOM.WW.ScadaBridge.NotificationOutbox/NotificationOutboxActor.cs

@@ -122,6 +122,7 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
         Receive<DiscardNotificationRequest>(HandleDiscard);
         Receive<NotificationKpiRequest>(HandleKpiRequest);
         Receive<PerSiteNotificationKpiRequest>(HandlePerSiteKpiRequest);
+        Receive<PerNodeNotificationKpiRequest>(HandlePerNodeKpiRequest);
     }
 
     /// <inheritdoc />
@@ -1081,6 +1082,38 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
         return new PerSiteNotificationKpiResponse(correlationId, Success: true, ErrorMessage: null, sites);
     }
 
+    /// <summary>
+    /// Handles a per-node KPI request, computing the per-source-node outbox metrics with the
+    /// same stuck cutoff and delivered window as <see cref="HandleKpiRequest"/>. Additive
+    /// alongside <see cref="HandlePerSiteKpiRequest"/> — does not change per-site behaviour.
+    /// </summary>
+    private void HandlePerNodeKpiRequest(PerNodeNotificationKpiRequest request)
+    {
+        var sender = Sender;
+        var now = DateTimeOffset.UtcNow;
+        var stuckCutoff = StuckCutoff(now);
+        var deliveredSince = now - _options.DeliveredKpiWindow;
+
+        ComputePerNodeKpisAsync(request.CorrelationId, stuckCutoff, deliveredSince).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new PerNodeNotificationKpiResponse(
+                request.CorrelationId,
+                Success: false,
+                ErrorMessage: ex.GetBaseException().Message,
+                Nodes: Array.Empty<NodeNotificationKpiSnapshot>()));
+    }
+
+    private async Task<PerNodeNotificationKpiResponse> ComputePerNodeKpisAsync(
+        string correlationId, DateTimeOffset stuckCutoff, DateTimeOffset deliveredSince)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var nodes = await repository.ComputePerNodeKpisAsync(stuckCutoff, deliveredSince);
+
+        return new PerNodeNotificationKpiResponse(correlationId, Success: true, ErrorMessage: null, nodes);
+    }
+
     /// <summary>
     /// The instant before which a still-pending notification counts as stuck — <paramref name="now"/>
     /// offset back by <see cref="NotificationOutboxOptions.StuckAgeThreshold"/>.