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.CentralUI/Components/Pages/Monitoring/Health.razor

@@ -71,6 +71,10 @@
                             <span class="badge bg-danger me-2">Offline</span>
                         }
                         <strong>@siteId</strong>
+                        @if (state.LatestReport?.NodeRole != null)
+                        {
+                            <span class="badge @(state.LatestReport.NodeRole == "Active" ? "bg-primary" : "bg-secondary") ms-2">@state.LatestReport.NodeRole</span>
+                        }
                     </div>
                     <small class="text-muted">
                         Last report: @state.LastReportReceivedAt.LocalDateTime.ToString("HH:mm:ss") | Seq: @state.LastSequenceNumber