feat(adminui): FleetStatusSignalRBridge — DPS → SignalR forwarding (F16)

New per-admin-node actor that subscribes to the fleet-status DistributedPubSub
topic + forwards every FleetStatusChanged snapshot to all SignalR clients
connected to FleetStatusHub via IHubContext.

Wired via WithOtOpcUaSignalRBridges (new AkkaConfigurationBuilder extension in
AdminUI.Hubs) — Program.cs calls it inside the if(hasAdmin) block alongside
WithOtOpcUaControlPlaneSingletons.

Per-node subscription rather than cluster-singleton: every admin node forwards
its own snapshots to its own connected clients. Simpler than singleton
coordination + acceptable because the messages are small and SignalR fan-out
is per-node anyway.

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

@@ -0,0 +1,52 @@
+using Akka.Actor;
+using Akka.Cluster.Tools.PublishSubscribe;
+using Akka.Event;
+using Microsoft.AspNetCore.SignalR;
+using ZB.MOM.WW.OtOpcUa.Commons.Messages.Fleet;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;
+
+/// <summary>
+/// Akka actor that subscribes to the <c>fleet-status</c> DistributedPubSub topic and forwards
+/// every <see cref="FleetStatusChanged"/> snapshot to all SignalR clients connected to
+/// <see cref="FleetStatusHub"/>. Spawned on admin-role nodes by
+/// <c>AddOtOpcUaSignalRBridges</c>.
+///
+/// The bridge runs locally on each admin node — every node that hosts the hub also forwards
+/// snapshots to its own connected clients. That keeps the hub-to-actor wiring simple (no
+/// cluster-singleton coordination needed) at the cost of duplicated DPS subscriptions on
+/// multi-admin deployments. Acceptable since the messages are small + the SignalR fan-out
+/// is per-node anyway.
+/// </summary>
+public sealed class FleetStatusSignalRBridge : ReceiveActor
+{
+    public const string TopicName = "fleet-status";
+
+    private readonly IHubContext<FleetStatusHub> _hub;
+    private readonly ILoggingAdapter _log = Context.GetLogger();
+
+    public static Props Props(IHubContext<FleetStatusHub> hub) =>
+        Akka.Actor.Props.Create(() => new FleetStatusSignalRBridge(hub));
+
+    public FleetStatusSignalRBridge(IHubContext<FleetStatusHub> hub)
+    {
+        _hub = hub;
+        ReceiveAsync<FleetStatusChanged>(ForwardAsync);
+        Receive<SubscribeAck>(_ => { /* DPS confirmation */ });
+    }
+
+    protected override void PreStart() =>
+        DistributedPubSub.Get(Context.System).Mediator.Tell(new Subscribe(TopicName, Self));
+
+    private async Task ForwardAsync(FleetStatusChanged msg)
+    {
+        try
+        {
+            await _hub.Clients.All.SendAsync(FleetStatusHub.MethodName, msg);
+        }
+        catch (Exception ex)
+        {
+            _log.Warning(ex, "FleetStatusSignalRBridge: SignalR push failed (count={Count})", msg.Nodes.Count);
+        }
+    }
+}

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

@@ -0,0 +1,39 @@
+using Akka.Actor;
+using Akka.Hosting;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;
+
+public static class HubServiceCollectionExtensions
+{
+    public const string FleetStatusSignalRBridgeName = "fleet-status-signalr-bridge";
+
+    /// <summary>
+    /// Spawns the SignalR bridge actors that forward DPS messages to browser-facing SignalR
+    /// hubs. Currently: <see cref="FleetStatusSignalRBridge"/> (DPS <c>fleet-status</c> topic →
+    /// <see cref="FleetStatusHub"/> clients).
+    ///
+    /// Call inside the admin-role configurator on the shared <see cref="AkkaConfigurationBuilder"/>:
+    /// <code>
+    /// if (hasAdmin)
+    /// {
+    ///     ab.WithOtOpcUaControlPlaneSingletons();
+    ///     ab.WithOtOpcUaSignalRBridges();
+    /// }
+    /// </code>
+    /// </summary>
+    public static AkkaConfigurationBuilder WithOtOpcUaSignalRBridges(this AkkaConfigurationBuilder builder)
+    {
+        builder.WithActors((system, registry, resolver) =>
+        {
+            var hub = resolver.GetService<IHubContext<FleetStatusHub>>();
+            var actor = system.ActorOf(FleetStatusSignalRBridge.Props(hub), FleetStatusSignalRBridgeName);
+            registry.Register<FleetStatusSignalRBridgeKey>(actor);
+        });
+        return builder;
+    }
+}
+
+/// <summary>Marker key for <see cref="ActorRegistry"/> lookup of the SignalR bridge actor.</summary>
+public sealed class FleetStatusSignalRBridgeKey { }

src/Server/ZB.MOM.WW.OtOpcUa.Host/Program.cs

@@ -44,7 +44,10 @@ builder.Services.AddAkka("otopcua", (ab, sp) =>
 {
     ab.WithOtOpcUaClusterBootstrap(sp);
     if (hasAdmin)
+    {
         ab.WithOtOpcUaControlPlaneSingletons();
+        ab.WithOtOpcUaSignalRBridges();
+    }
     if (hasDriver)
         ab.WithOtOpcUaRuntimeActors();
 });