fix(siteruntime): capture Self before Task.Run in artifact deploy; seed MxGateway connections

- DeploymentManagerActor.HandleDeployArtifacts read the Self property inside its
  Task.Run lambda (line dispatching ApplyArtifactDataConnectionsToDcl). Self is
  backed by the ambient ActorCell, null on a thread-pool thread, so it threw
  'no active ActorContext' — surfaced the first time a data connection is
  deployed via deploy-artifacts. Capture Self into a local first (as Sender
  already was).
- seed-sites.sh: create a shared MxGateway data connection (10.100.0.48:5120)
  on each site and deploy artifacts so the DCL establishes them.
- build.sh: nounset-safe empty-array expansion (bash 3.2).

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

@@ -1002,6 +1002,11 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
             "Deploying system artifacts, deploymentId={DeploymentId}", command.DeploymentId);
 
         var sender = Sender;
+        // Capture Self before entering Task.Run: the Self/Sender/Context properties
+        // are backed by the ambient ActorCell, which is null on a thread-pool thread,
+        // so reading Self *inside* the lambda throws "no active ActorContext". The
+        // data-connections branch below dispatches via this captured ref.
+        var self = Self;
 
         Task.Run(async () =>
         {
@@ -1071,7 +1076,7 @@ public class DeploymentManagerActor : ReceiveActor, IWithTimers
                     // helper's hash cache skips unchanged definitions, so
                     // the push is idempotent for re-deploys of the same
                     // artifact bundle.
-                    Self.Tell(new ApplyArtifactDataConnectionsToDcl(command.DataConnections));
+                    self.Tell(new ApplyArtifactDataConnectionsToDcl(command.DataConnections));
                 }
 
                 // Store SMTP configurations