feat: bridge ActorSystem into DI (transient) for shared health checks

src/ZB.MOM.WW.ScadaBridge.Host/Program.cs

@@ -120,6 +120,13 @@ try
         builder.Services.AddSingleton<AkkaHostedService>();
         builder.Services.AddHostedService(sp => sp.GetRequiredService<AkkaHostedService>());
 
+        // The shared ZB.MOM.WW.Health Akka checks resolve ActorSystem from DI. ScadaBridge owns the
+        // ActorSystem inside AkkaHostedService (not a DI singleton), so bridge it as TRANSIENT: each
+        // resolve re-reads the current value — null while warming up (checks → Degraded), live after.
+        // The factory must NOT throw: GetService<ActorSystem>() must return null (not raise) pre-start.
+        builder.Services.AddTransient<Akka.Actor.ActorSystem>(sp =>
+            sp.GetRequiredService<AkkaHostedService>().ActorSystem!);
+
         // InboundAPI-022: register the production IActiveNodeGate implementation so
         // standby-node gating is actually enforced (the InboundApiEndpointFilter
         // consults IActiveNodeGate and defaults to "allow" when none is registered,

src/ZB.MOM.WW.ScadaBridge.Host/SiteServiceRegistration.cs

@@ -73,6 +73,13 @@ public static class SiteServiceRegistration
         services.AddSingleton<AkkaHostedService>();
         services.AddHostedService(sp => sp.GetRequiredService<AkkaHostedService>());
 
+        // The shared ZB.MOM.WW.Health Akka checks resolve ActorSystem from DI. ScadaBridge owns the
+        // ActorSystem inside AkkaHostedService (not a DI singleton), so bridge it as TRANSIENT: each
+        // resolve re-reads the current value — null while warming up (checks → Degraded), live after.
+        // The factory must NOT throw: GetService<ActorSystem>() must return null (not raise) pre-start.
+        services.AddTransient<Akka.Actor.ActorSystem>(sp =>
+            sp.GetRequiredService<AkkaHostedService>().ActorSystem!);
+
         // Cluster node status provider for health reports
         services.AddSingleton<IClusterNodeProvider>(sp =>
         {