feat(notification-outbox): add CommunicationService outbox methods

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -288,6 +288,10 @@ akka {{
         // Hand the outbox proxy to the CentralCommunicationActor so forwarded
         // NotificationSubmit messages from sites are routed to the outbox singleton.
         centralCommActor.Tell(new RegisterNotificationOutbox(outboxProxy));
+
+        // Hand the same proxy to the CommunicationService so the Central UI can
+        // Ask the outbox actor directly (query, retry, discard, KPIs).
+        commService?.SetNotificationOutbox(outboxProxy);
         _logger.LogInformation("NotificationOutbox singleton created and registered with CentralCommunicationActor");
 
         _logger.LogInformation("Central actors registered. CentralCommunicationActor created.");