feat(notification-outbox): forward site S&F notifications to central

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -422,15 +422,18 @@ akka {{
                         .GetRequiredService<ScadaLink.ExternalSystemGateway.DatabaseGateway>()
                         .DeliverBufferedAsync(msg);
                 });
+            // Notification Outbox: a buffered notification is no longer delivered by
+            // the site over SMTP. "Delivering" it means forwarding it to the central
+            // cluster via the SiteCommunicationActor and treating central's
+            // NotificationSubmitAck as the outcome (accepted → delivered; not accepted
+            // or timeout → throw → transient → keep buffering). Central owns SMTP.
+            var notificationForwarder = new ScadaLink.StoreAndForward.NotificationForwarder(
+                siteCommActor,
+                _nodeOptions.SiteId!,
+                _communicationOptions.NotificationForwardTimeout);
             storeAndForwardService.RegisterDeliveryHandler(
                 ScadaLink.Commons.Types.Enums.StoreAndForwardCategory.Notification,
-                async msg =>
-                {
-                    using var scope = _serviceProvider.CreateScope();
-                    return await scope.ServiceProvider
-                        .GetRequiredService<ScadaLink.NotificationService.NotificationDeliveryService>()
-                        .DeliverBufferedAsync(msg);
-                });
+                notificationForwarder.DeliverAsync);
             _logger.LogInformation(
                 "Store-and-forward delivery handlers registered (ExternalSystem, CachedDbWrite, Notification)");