test(central-ui): cover the per-site KPI error path on the Notification KPIs page

tests/ScadaLink.CentralUI.Tests/Pages/NotificationKpisPageTests.cs

@@ -113,6 +113,24 @@ public class NotificationKpisPageTests : BunitContext
         cut.WaitForAssertion(() => Assert.Contains("kpi down", cut.Markup));
     }
 
+    [Fact]
+    public void ShowsPerSiteError_WhenPerSiteKpiQueryFails()
+    {
+        // Only the per-site path errors — the global KPI reply stays successful.
+        _perSiteReply = new PerSiteNotificationKpiResponse(
+            "p", false, "per-site down", new List<SiteNotificationKpiSnapshot>());
+
+        var cut = Render<NotificationKpisPage>();
+
+        cut.WaitForAssertion(() =>
+        {
+            Assert.Contains("Per-site KPIs unavailable: per-site down", cut.Markup);
+            // The two error paths are isolated — the global KPI alert (whose markup
+            // opens ">KPIs unavailable:", without the "Per-site " prefix) must not appear.
+            Assert.DoesNotContain(">KPIs unavailable:", cut.Markup);
+        });
+    }
+
     [Fact]
     public void ShowsPerSiteEmptyState_WhenNoSites()
     {