fix(dcl): route native alarm subscribe/unsubscribe through DataConnectionManagerActor

The NativeAlarmActor sends SubscribeAlarmsRequest to the DCL manager, but the
manager only routed tag/write/browse messages to the per-connection
DataConnectionActor — alarm subscribe/unsubscribe were unhandled and dead-lettered,
so native alarms never subscribed at runtime. Caught by live T28 deployment.
Mirrors the existing HandleRoute forwarding.

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Actors/DataConnectionManagerActor.cs

@@ -43,6 +43,8 @@ public class DataConnectionManagerActor : ReceiveActor
         Receive<CreateConnectionCommand>(HandleCreateConnection);
         Receive<SubscribeTagsRequest>(HandleRoute);
         Receive<UnsubscribeTagsRequest>(HandleRoute);
+        Receive<SubscribeAlarmsRequest>(HandleRouteAlarms);
+        Receive<UnsubscribeAlarmsRequest>(HandleRouteAlarms);
         Receive<WriteTagRequest>(HandleRouteWrite);
         Receive<RemoveConnectionCommand>(HandleRemoveConnection);
         Receive<GetAllHealthReports>(HandleGetAllHealthReports);
@@ -101,6 +103,31 @@ public class DataConnectionManagerActor : ReceiveActor
             _log.Warning("No connection actor for {0} during unsubscribe", request.ConnectionName);
     }
 
+    /// <summary>
+    /// Routes a native alarm subscribe to the <see cref="DataConnectionActor"/> that owns
+    /// the named connection (the NativeAlarmActor sends here, not to the child directly).
+    /// </summary>
+    private void HandleRouteAlarms(SubscribeAlarmsRequest request)
+    {
+        if (_connectionActors.TryGetValue(request.ConnectionName, out var actor))
+            actor.Forward(request);
+        else
+        {
+            _log.Warning("No connection actor for {0} during alarm subscribe", request.ConnectionName);
+            Sender.Tell(new SubscribeAlarmsResponse(
+                request.CorrelationId, request.InstanceUniqueName, false,
+                $"Unknown connection: {request.ConnectionName}", DateTimeOffset.UtcNow));
+        }
+    }
+
+    private void HandleRouteAlarms(UnsubscribeAlarmsRequest request)
+    {
+        if (_connectionActors.TryGetValue(request.ConnectionName, out var actor))
+            actor.Forward(request);
+        else
+            _log.Warning("No connection actor for {0} during alarm unsubscribe", request.ConnectionName);
+    }
+
     private void HandleRouteWrite(WriteTagRequest request)
     {
         if (_connectionActors.TryGetValue(request.ConnectionName, out var actor))

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

@@ -58,6 +58,23 @@ public class DataConnectionManagerActorTests : TestKit
         Assert.Contains("Unknown connection", response.ErrorMessage);
     }
 
+    [Fact]
+    public void SubscribeAlarmsToUnknownConnection_ReturnsError()
+    {
+        // Regression for the live integration gap: the NativeAlarmActor sends
+        // SubscribeAlarmsRequest to the DCL manager, which must route it to the
+        // named connection actor (or reply with an error) — not dead-letter it.
+        var manager = Sys.ActorOf(Props.Create(() =>
+            new DataConnectionManagerActor(_mockFactory, _options, _mockHealthCollector)));
+
+        manager.Tell(new SubscribeAlarmsRequest(
+            "corr1", "inst1", "nonexistent", "ns=2;s=Tank01", null, DateTimeOffset.UtcNow));
+
+        var response = ExpectMsg<SubscribeAlarmsResponse>();
+        Assert.False(response.Success);
+        Assert.Contains("Unknown connection", response.ErrorMessage);
+    }
+
     [Fact]
     public async Task DCL002_ConnectionActorCrash_PreservesSubscriptionState()
     {