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/Adapters/LmxProxyDataConnection.cs

@@ -23,6 +23,7 @@ public class LmxProxyDataConnection : IDataConnection
     private ConnectionHealth _status = ConnectionHealth.Disconnected;
 
     private readonly Dictionary<string, ILmxSubscription> _subscriptions = new();
+    private volatile bool _disconnectFired;
 
     public LmxProxyDataConnection(ILmxProxyClientFactory clientFactory, ILogger<LmxProxyDataConnection> logger)
     {
@@ -31,6 +32,7 @@ public class LmxProxyDataConnection : IDataConnection
     }
 
     public ConnectionHealth Status => _status;
+    public event Action? Disconnected;
 
     public async Task ConnectAsync(IDictionary<string, string> connectionDetails, CancellationToken cancellationToken = default)
     {
@@ -39,11 +41,15 @@ public class LmxProxyDataConnection : IDataConnection
             _port = port;
         connectionDetails.TryGetValue("ApiKey", out var apiKey);
 
+        var samplingIntervalMs = connectionDetails.TryGetValue("SamplingIntervalMs", out var sampStr) && int.TryParse(sampStr, out var samp) ? samp : 0;
+        var useTls = connectionDetails.TryGetValue("UseTls", out var tlsStr) && bool.TryParse(tlsStr, out var tls) && tls;
+
         _status = ConnectionHealth.Connecting;
-        _client = _clientFactory.Create(_host, _port, apiKey);
+        _client = _clientFactory.Create(_host, _port, apiKey, samplingIntervalMs, useTls);
 
         await _client.ConnectAsync(cancellationToken);
         _status = ConnectionHealth.Connected;
+        _disconnectFired = false;
 
         _logger.LogInformation("LmxProxy connected to {Host}:{Port}", _host, _port);
     }
@@ -62,13 +68,22 @@ public class LmxProxyDataConnection : IDataConnection
     {
         EnsureConnected();
 
-        var vtq = await _client!.ReadAsync(tagPath, cancellationToken);
-        var quality = MapQuality(vtq.Quality);
-        var tagValue = new TagValue(vtq.Value, quality, new DateTimeOffset(vtq.TimestampUtc, TimeSpan.Zero));
+        try
+        {
+            var vtq = await _client!.ReadAsync(tagPath, cancellationToken);
+            var quality = MapQuality(vtq.Quality);
+            var tagValue = new TagValue(vtq.Value, quality, new DateTimeOffset(vtq.TimestampUtc, TimeSpan.Zero));
 
-        return vtq.Quality == LmxQuality.Bad
-            ? new ReadResult(false, tagValue, "LmxProxy read returned bad quality")
-            : new ReadResult(true, tagValue, null);
+            return vtq.Quality == LmxQuality.Bad
+                ? new ReadResult(false, tagValue, "LmxProxy read returned bad quality")
+                : new ReadResult(true, tagValue, null);
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            _logger.LogWarning(ex, "LmxProxy read failed for {TagPath} — connection may be lost", tagPath);
+            RaiseDisconnected();
+            throw;
+        }
     }
 
     public async Task<IReadOnlyDictionary<string, ReadResult>> ReadBatchAsync(IEnumerable<string> tagPaths, CancellationToken cancellationToken = default)
@@ -161,6 +176,11 @@ public class LmxProxyDataConnection : IDataConnection
                 var quality = MapQuality(vtq.Quality);
                 callback(path, new TagValue(vtq.Value, quality, new DateTimeOffset(vtq.TimestampUtc, TimeSpan.Zero)));
             },
+            onStreamError: () =>
+            {
+                _logger.LogWarning("LmxProxy subscription stream ended unexpectedly for {TagPath}", tagPath);
+                RaiseDisconnected();
+            },
             cancellationToken);
 
         var subscriptionId = Guid.NewGuid().ToString("N");
@@ -199,6 +219,19 @@ public class LmxProxyDataConnection : IDataConnection
             throw new InvalidOperationException("LmxProxy client is not connected.");
     }
 
+    /// <summary>
+    /// Marks the connection as disconnected and fires the Disconnected event once.
+    /// Thread-safe: only the first caller triggers the event.
+    /// </summary>
+    private void RaiseDisconnected()
+    {
+        if (_disconnectFired) return;
+        _disconnectFired = true;
+        _status = ConnectionHealth.Disconnected;
+        _logger.LogWarning("LmxProxy connection to {Host}:{Port} lost", _host, _port);
+        Disconnected?.Invoke();
+    }
+
     private static QualityCode MapQuality(LmxQuality quality) => quality switch
     {
         LmxQuality.Good => QualityCode.Good,