feat(gateway): forward operator credentials on alarm acknowledgement

Claude-Session: https://claude.ai/code/session_016J6isfcgqy4SB2RK3ZvFvT

src/ZB.MOM.WW.MxGateway.Server/Configuration/AlarmsOptions.cs

@@ -73,6 +73,13 @@ public sealed class AlarmsOptions
     /// </summary>
     public int MaxAlarmsPerFetch { get; init; } = 1024;
 
+    /// <summary>
+    ///     MXAccess client name the alarm worker's ack writer registers with. The
+    ///     AVEVA Historian records it as each acknowledgement's OperatorNode.
+    ///     Conveyed to workers via MXGATEWAY_ALARM_ACK_CLIENT_NAME.
+    /// </summary>
+    public string AckClientName { get; init; } = "MxGateway";
+
     /// <summary>
     ///     Configuration for the alarm-manager ↔ subtag fallback mechanism:
     ///     operating mode, failure-detection thresholds, discovery, and subtag