feat(notif-outbox): add SourceNode to Notification entity + NotificationSubmit

src/ScadaLink.Commons/Entities/Notifications/Notification.cs

@@ -25,6 +25,15 @@ public class Notification
     /// <summary>Resolved delivery targets snapshotted at delivery time, for audit.</summary>
     public string? ResolvedTargets { get; set; }
     public string SourceSiteId { get; set; }
+
+    /// <summary>
+    /// The cluster node on which the notification was emitted — `node-a` / `node-b`
+    /// for site rows (qualified by <see cref="SourceSiteId"/>), `central-a` / `central-b`
+    /// for central-originated rows. Carried from the site on the
+    /// <see cref="Commons.Messages.Notification.NotificationSubmit"/> and persisted at
+    /// central; nullable so rows submitted before the column existed don't block ingest.
+    /// </summary>
+    public string? SourceNode { get; set; }
     public string? SourceInstanceId { get; set; }
     public string? SourceScript { get; set; }
 

src/ScadaLink.Commons/Messages/Notification/NotificationMessages.cs

@@ -18,6 +18,15 @@ namespace ScadaLink.Commons.Messages.Notification;
 /// <c>NotifyDeliver</c> audit rows. Additive trailing member — null for messages built
 /// before the field existed, or for non-routed runs.
 /// </param>
+/// <param name="SourceNode">
+/// The cluster node on which the notification was emitted — `node-a` / `node-b` for site
+/// submissions, `central-a` / `central-b` for central-originated rows. Stamped by the
+/// emitting node from <c>INodeIdentityProvider</c> and carried, inside the serialized
+/// payload, through the site store-and-forward buffer so the central dispatcher can
+/// persist it on the <c>Notifications</c> row and echo it onto the <c>NotifyDeliver</c>
+/// audit rows. Additive trailing member — null for messages built before the field
+/// existed.
+/// </param>
 public record NotificationSubmit(
     string NotificationId,
     string ListName,
@@ -28,7 +37,8 @@ public record NotificationSubmit(
     string? SourceScript,
     DateTimeOffset SiteEnqueuedAt,
     Guid? OriginExecutionId = null,
-    Guid? OriginParentExecutionId = null);
+    Guid? OriginParentExecutionId = null,
+    string? SourceNode = null);
 
 /// <summary>
 /// Central -> Site: ack sent after the notification row is persisted.