feat(runtime): publish DriverHealthChanged via DriverInstanceActor

- IDriverHealthPublisher in Core.Abstractions + NullDriverHealthPublisher
  no-op for tests/dev-stub paths.
- AkkaDriverHealthPublisher in Runtime forwards to the cluster-wide
  `driver-health` DPS topic.
- DriverInstanceActor instrumented to publish snapshots on every
  observable state change + a periodic 30s heartbeat so the AdminUI
  snapshot store warms up for newly-joined SignalR clients.
- Sliding 5-minute Faulted-count tracked per actor via Queue<DateTime>.
- DriverHostActor.SpawnChild threads clusterId (_localNode.Value) and
  the health publisher down to every DriverInstanceActor child.
- ServiceCollectionExtensions.AddOtOpcUaRuntime registers
  AkkaDriverHealthPublisher as IDriverHealthPublisher singleton.

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ServiceCollectionExtensions.cs

@@ -42,6 +42,7 @@ public static class ServiceCollectionExtensions
         services.TryAddSingleton<IDriverFactory>(NullDriverFactory.Instance);
         services.TryAddSingleton<IOpcUaAddressSpaceSink>(NullOpcUaAddressSpaceSink.Instance);
         services.TryAddSingleton<IServiceLevelPublisher>(NullServiceLevelPublisher.Instance);
+        services.TryAddSingleton<IDriverHealthPublisher, AkkaDriverHealthPublisher>();
         return services;
     }
 
@@ -87,6 +88,7 @@ public static class ServiceCollectionExtensions
             var addressSpaceSink = resolver.GetService<IOpcUaAddressSpaceSink>() ?? NullOpcUaAddressSpaceSink.Instance;
             var serviceLevel = resolver.GetService<IServiceLevelPublisher>() ?? NullServiceLevelPublisher.Instance;
             var loggerFactory = resolver.GetService<ILoggerFactory>() ?? NullLoggerFactory.Instance;
+            var healthPublisher = resolver.GetService<IDriverHealthPublisher>() ?? NullDriverHealthPublisher.Instance;
 
             var dbHealth = system.ActorOf(
                 DbHealthProbeActor.Props(dbFactory),
@@ -116,7 +118,8 @@ public static class ServiceCollectionExtensions
                 DriverHostActor.Props(dbFactory, roleInfo.LocalNode, coordinator: null,
                     driverFactory: driverFactory, localRoles: roleInfo.LocalRoles,
                     dependencyMux: mux,
-                    opcUaPublishActor: publishActor),
+                    opcUaPublishActor: publishActor,
+                    healthPublisher: healthPublisher),
                 DriverHostActorName);
             registry.Register<DriverHostActorKey>(driverHost);