feat(scadabridge): wire AddZbTelemetry + /metrics in both composition roots

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

@@ -11,6 +11,7 @@ using ZB.MOM.WW.ScadaBridge.NotificationService;
 using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
 using ZB.MOM.WW.ScadaBridge.SiteRuntime;
 using ZB.MOM.WW.ScadaBridge.StoreAndForward;
+using ZB.MOM.WW.Telemetry;
 
 namespace ZB.MOM.WW.ScadaBridge.Host;
 
@@ -114,5 +115,19 @@ public static class SiteServiceRegistration
         // writers so they can stamp the SourceNode column. Registered here in
         // shared bootstrap because every node (central + site) needs it.
         services.AddSingleton<INodeIdentityProvider, NodeIdentityProvider>();
+
+        // Observability — shared ZB.MOM.WW.Telemetry. Registered in shared bootstrap so
+        // BOTH the central and site composition roots wire the OTel Resource (the
+        // service.name/site.id/node.role identity triple) + standard instrumentation +
+        // the always-on Prometheus exporter. Mount the /metrics scrape endpoint per role
+        // with app.MapZbMetrics(). The same `?? "central"` SiteId default Program.cs uses
+        // is applied here so the Resource attribute matches the log-enricher value.
+        // Meters left empty — application instruments are a deferred follow-on.
+        services.AddZbTelemetry(o =>
+        {
+            o.ServiceName = "scadabridge";
+            o.SiteId = config["ScadaBridge:Node:SiteId"] ?? "central";
+            o.NodeRole = config["ScadaBridge:Node:Role"];
+        });
     }
 }