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.Communication/CommunicationService.cs

@@ -161,6 +161,22 @@ public class CommunicationService
             envelope, _options.QueryTimeout, cancellationToken);
     }
 
+    public async Task<ParkedMessageRetryResponse> RetryParkedMessageAsync(
+        string siteId, ParkedMessageRetryRequest request, CancellationToken cancellationToken = default)
+    {
+        var envelope = new SiteEnvelope(siteId, request);
+        return await GetActor().Ask<ParkedMessageRetryResponse>(
+            envelope, _options.QueryTimeout, cancellationToken);
+    }
+
+    public async Task<ParkedMessageDiscardResponse> DiscardParkedMessageAsync(
+        string siteId, ParkedMessageDiscardRequest request, CancellationToken cancellationToken = default)
+    {
+        var envelope = new SiteEnvelope(siteId, request);
+        return await GetActor().Ask<ParkedMessageDiscardResponse>(
+            envelope, _options.QueryTimeout, cancellationToken);
+    }
+
     // ── Pattern 8: Heartbeat (site→central, Tell) ──
     // Heartbeats are received by central, not sent. No method needed here.