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

tests/ScadaLink.HealthMonitoring.Tests/HealthReportSenderTests.cs

@@ -23,6 +23,7 @@ public class HealthReportSenderTests
     {
         var transport = new FakeTransport();
         var collector = new SiteHealthCollector();
+        collector.SetActiveNode(true);
         var options = Options.Create(new HealthMonitoringOptions
         {
             ReportInterval = TimeSpan.FromMilliseconds(50)
@@ -61,6 +62,7 @@ public class HealthReportSenderTests
     {
         var transport = new FakeTransport();
         var collector = new SiteHealthCollector();
+        collector.SetActiveNode(true);
         var options = Options.Create(new HealthMonitoringOptions
         {
             ReportInterval = TimeSpan.FromMilliseconds(50)
@@ -91,6 +93,7 @@ public class HealthReportSenderTests
     {
         var transport = new FakeTransport();
         var collector = new SiteHealthCollector();
+        collector.SetActiveNode(true);
         var options = Options.Create(new HealthMonitoringOptions
         {
             ReportInterval = TimeSpan.FromMilliseconds(50)