feat(adminui): add connection-health signal to in-process broadcaster + bridges

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Hubs/AlertSignalRBridge.cs

@@ -38,13 +38,22 @@ public sealed class AlertSignalRBridge : ReceiveActor
         _hub = hub;
         _broadcaster = broadcaster;
         ReceiveAsync<AlarmTransitionEvent>(ForwardAsync);
-        Receive<SubscribeAck>(_ => { /* DPS confirmation */ });
+        // DPS subscription is now live — mark the feed connected so the Blazor "live" pill lights up.
+        Receive<SubscribeAck>(_ => _broadcaster.SetConnected(true));
     }
 
     /// <inheritdoc />
     protected override void PreStart() =>
         DistributedPubSub.Get(Context.System).Mediator.Tell(new Subscribe(TopicName, Self));
 
+    /// <inheritdoc />
+    protected override void PostStop()
+    {
+        // Bridge stopping — the feed is no longer live, drop the "live" pill.
+        _broadcaster.SetConnected(false);
+        base.PostStop();
+    }
+
     private async Task ForwardAsync(AlarmTransitionEvent msg)
     {
         // In-process fan-out first — this is what the Blazor Server Alerts page reads. The hub push