feat(dcl): OPC UA Alarms & Conditions adapter (event subscription + ConditionRefresh)

Adds IAlarmSubscribableConnection to OpcUaDataConnection, IOpcUaClient alarm
subscription methods, and RealOpcUaClient A&C event monitored-item +
EventFilter + ConditionRefresh snapshot, mapping fields via OpcUaAlarmMapper.
Behavior verified against a live A&C server in Task 28; mapper unit-tested.

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/IOpcUaClient.cs

@@ -1,4 +1,5 @@
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Protocol;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
 
 namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
 
@@ -81,6 +82,22 @@ public interface IOpcUaClient : IAsyncDisposable
     /// <returns>A task representing the asynchronous operation.</returns>
     Task RemoveSubscriptionAsync(string subscriptionHandle, CancellationToken cancellationToken = default);
 
+    /// <summary>
+    /// Subscribes to OPC UA Alarms &amp; Conditions events under
+    /// <paramref name="sourceNodeId"/> (or the Server object when null). On
+    /// (re)subscribe the adapter issues a ConditionRefresh and replays the
+    /// active conditions as Snapshot…SnapshotComplete transitions. Returns a
+    /// handle for <see cref="RemoveAlarmSubscriptionAsync"/>.
+    /// </summary>
+    Task<string> CreateAlarmSubscriptionAsync(
+        string? sourceNodeId,
+        string? conditionFilter,
+        Action<NativeAlarmTransition> onTransition,
+        CancellationToken cancellationToken = default);
+
+    /// <summary>Removes an alarm-event subscription by handle.</summary>
+    Task RemoveAlarmSubscriptionAsync(string subscriptionHandle, CancellationToken cancellationToken = default);
+
     /// <summary>
     /// Reads the current value of a node.
     /// </summary>
@@ -182,6 +199,19 @@ internal class StubOpcUaClient : IOpcUaClient
         return Task.CompletedTask;
     }
 
+    /// <inheritdoc />
+    public Task<string> CreateAlarmSubscriptionAsync(
+        string? sourceNodeId, string? conditionFilter,
+        Action<NativeAlarmTransition> onTransition, CancellationToken cancellationToken = default)
+    {
+        // Stub: no events. Real A&C subscription lives in RealOpcUaClient.
+        return Task.FromResult(Guid.NewGuid().ToString());
+    }
+
+    /// <inheritdoc />
+    public Task RemoveAlarmSubscriptionAsync(string subscriptionHandle, CancellationToken cancellationToken = default)
+        => Task.CompletedTask;
+
     /// <inheritdoc />
     public Task<(object? Value, DateTime SourceTimestamp, uint StatusCode)> ReadValueAsync(
         string nodeId, CancellationToken cancellationToken = default)