feat(notification-outbox): per-site KPI request/response message contracts

tests/ScadaLink.Commons.Tests/Messages/NotificationMessagesTests.cs

@@ -1,4 +1,5 @@
 using ScadaLink.Commons.Messages.Notification;
+using ScadaLink.Commons.Types.Notifications;
 
 namespace ScadaLink.Commons.Tests.Messages;
 
@@ -187,4 +188,26 @@ public class NotificationMessagesTests
         var msg = new NotificationKpiRequest("corr-1");
         Assert.Equal("corr-1", msg.CorrelationId);
     }
+
+    [Fact]
+    public void PerSiteNotificationKpiRequest_CarriesCorrelationId()
+    {
+        var request = new PerSiteNotificationKpiRequest("corr-1");
+        Assert.Equal("corr-1", request.CorrelationId);
+    }
+
+    [Fact]
+    public void PerSiteNotificationKpiResponse_CarriesPerSiteSnapshots()
+    {
+        var sites = new[]
+        {
+            new SiteNotificationKpiSnapshot("plant-a", 3, 1, 0, 10, TimeSpan.FromMinutes(4)),
+        };
+        var response = new PerSiteNotificationKpiResponse("corr-1", Success: true, ErrorMessage: null, sites);
+
+        Assert.True(response.Success);
+        Assert.Null(response.ErrorMessage);
+        Assert.Single(response.Sites);
+        Assert.Equal("plant-a", response.Sites[0].SourceSiteId);
+    }
 }