feat: add JoeAppEngine OPC UA nodes, fix DCL auto-reconnect and quality push

- Add JoeAppEngine folder to OPC UA nodes.json (BTCS, AlarmCntsBySeverity, Scheduler/ScanTime)
- Fix DataConnectionActor: capture Self in PreStart for use from non-actor threads,
  preventing Self.Tell failure in Disconnected event handler
- Implement InstanceActor.HandleConnectionQualityChanged to mark attributes Bad on disconnect
- Fix LmxFakeProxy TagMapper to serialize arrays as JSON instead of "System.Int32[]"
- Allow DataType and DataSourceReference updates in TemplateService.UpdateAttributeAsync
- Update test_infra_opcua.md with JoeAppEngine documentation

src/ScadaLink.DataConnectionLayer/Actors/DataConnectionActor.cs

@@ -62,6 +62,12 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
 
     private readonly IDictionary<string, string> _connectionDetails;
 
+    /// <summary>
+    /// Captured Self reference for use from non-actor threads (event handlers, callbacks).
+    /// Akka.NET's Self property is only valid inside the actor's message loop.
+    /// </summary>
+    private IActorRef _self = null!;
+
     public DataConnectionActor(
         string connectionName,
         IDataConnection adapter,
@@ -79,13 +85,28 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
     protected override void PreStart()
     {
         _log.Info("DataConnectionActor [{0}] starting in Connecting state", _connectionName);
+
+        // Capture Self for use from non-actor threads (event handlers, callbacks).
+        // Akka.NET's Self property is only valid inside the actor's message loop.
+        _self = Self;
+
+        // Listen for unexpected adapter disconnections
+        _adapter.Disconnected += OnAdapterDisconnected;
+
         BecomeConnecting();
     }
 
+    private void OnAdapterDisconnected()
+    {
+        // Marshal the event onto the actor's message loop using captured _self reference.
+        // This runs on a background thread (gRPC stream reader), so Self would throw.
+        _self.Tell(new AdapterDisconnected());
+    }
+
     protected override void PostStop()
     {
         _log.Info("DataConnectionActor [{0}] stopping — disposing adapter", _connectionName);
-        // Clean up the adapter asynchronously
+        _adapter.Disconnected -= OnAdapterDisconnected;
         _ = _adapter.DisposeAsync().AsTask();
     }
 
@@ -276,7 +297,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
 
     private void HandleDisconnect()
     {
-        _log.Warning("[{0}] Adapter reported disconnect", _connectionName);
+        _log.Warning("[{0}] AdapterDisconnected message received — transitioning to Reconnecting", _connectionName);
         BecomeReconnecting();
     }