feat(dcl): register MxGateway protocol in factory + config flatten + options

DataConnectionFactory registers 'MxGateway' -> MxGatewayDataConnection over the
real client; AddDataConnectionLayer binds MxGatewayGlobalOptions; DeploymentManager
FlattenConnectionConfig gains an MxGateway arm using the typed serializer. Factory
test confirms Create("MxGateway") returns the adapter.

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/DataConnectionFactory.cs

@@ -38,6 +38,13 @@ public class DataConnectionFactory : IDataConnectionFactory
         RegisterAdapter("OpcUa", details => new OpcUaDataConnection(
             new RealOpcUaClientFactory(globalOptions, _loggerFactory),
             _loggerFactory.CreateLogger<OpcUaDataConnection>()));
+
+        // MxGateway: gRPC to the MxAccess Gateway. The RealMxGatewayClient wraps the
+        // ZB.MOM.WW.MxGateway.Client package; per-connection config arrives via the
+        // flat details dict (see MxGatewayEndpointConfigSerializer).
+        RegisterAdapter("MxGateway", details => new MxGatewayDataConnection(
+            new RealMxGatewayClientFactory(_loggerFactory),
+            _loggerFactory.CreateLogger<MxGatewayDataConnection>()));
     }
 
     /// <summary>

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/ServiceCollectionExtensions.cs

@@ -18,6 +18,9 @@ public static class ServiceCollectionExtensions
         services.AddOptions<OpcUaGlobalOptions>()
             .BindConfiguration("OpcUa");
 
+        services.AddOptions<MxGatewayGlobalOptions>()
+            .BindConfiguration("MxGateway");
+
         // WP-34: Register the factory for protocol extensibility
         services.AddSingleton<IDataConnectionFactory, DataConnectionFactory>();
 

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/DeploymentManagerActor.cs

@@ -767,6 +767,12 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
             return Commons.Serialization.OpcUaEndpointConfigSerializer.ToFlatDict(config);
         }
 
+        if (string.Equals(protocol, "MxGateway", StringComparison.OrdinalIgnoreCase))
+        {
+            var config = Commons.Serialization.MxGatewayEndpointConfigSerializer.Deserialize(json);
+            return Commons.Serialization.MxGatewayEndpointConfigSerializer.ToFlatDict(config);
+        }
+
         // Fallback: assume legacy flat-dict shape for any future / unknown protocol.
         try
         {

tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/DataConnectionFactoryTests.cs

@@ -18,6 +18,16 @@ public class DataConnectionFactoryTests
         Assert.IsType<OpcUaDataConnection>(connection);
     }
 
+    [Fact]
+    public void Create_MxGateway_ReturnsMxGatewayAdapter()
+    {
+        var factory = new DataConnectionFactory(NullLoggerFactory.Instance);
+
+        var connection = factory.Create("MxGateway", new Dictionary<string, string>());
+
+        Assert.IsType<MxGatewayDataConnection>(connection);
+    }
+
     [Fact]
     public void Create_CaseInsensitive()
     {