feat(mxgateway): export GatewayMetrics via AddZbTelemetry + /metrics (name/units unchanged)

src/ZB.MOM.WW.MxGateway.Server/GatewayApplication.cs

@@ -15,6 +15,7 @@ using ZB.MOM.WW.MxGateway.Server.Security.Authentication;
 using ZB.MOM.WW.MxGateway.Server.Security.Authorization;
 using ZB.MOM.WW.MxGateway.Server.Sessions;
 using ZB.MOM.WW.MxGateway.Server.Workers;
+using ZB.MOM.WW.Telemetry;
 using ZB.MOM.WW.Telemetry.Serilog;
 
 namespace ZB.MOM.WW.MxGateway.Server;
@@ -73,6 +74,11 @@ public static class GatewayApplication
                 failureStatus: null,
                 tags: new[] { ZbHealthTags.Ready });
         builder.Services.AddSingleton<GatewayMetrics>();
+        builder.AddZbTelemetry(o =>
+        {
+            o.ServiceName = "mxgateway";
+            o.Meters = [GatewayMetrics.MeterName]; // "MxGateway.Server" — name unchanged
+        });
         builder.Services.AddSingleton<ILogRedactor, GatewayLogRedactorSeam>();
         builder.Services.AddSingleton<MxAccessGrpcMapper>();
         builder.Services.AddSingleton<MxAccessGrpcRequestValidator>();
@@ -179,6 +185,7 @@ public static class GatewayApplication
         endpoints.MapStaticAssets(ResolveStaticAssetsManifestPath());
 
         endpoints.MapZbHealth();
+        endpoints.MapZbMetrics();
 
         endpoints.MapGrpcService<MxAccessGatewayService>();
         endpoints.MapGrpcService<GalaxyRepositoryGrpcService>();