Implement NotifyOnStatusChange feature for nodes and enhance Telegram notifications

- Added `NotifyOnStatusChange` property to the `Node` class and related DTOs to allow individual node configuration for status change notifications.
- Updated `NodeHealthCheckService` to send Telegram notifications to admins when a node's status changes, based on the new property.
- Enhanced the `ITelegramNotifier` interface with a method for notifying admins about node status changes.
- Modified the frontend to include a checkbox for `NotifyOnStatusChange` in the node editing dialog, allowing admins to easily configure this setting.
- Updated API documentation to reflect the new `notifyOnStatusChange` parameter in the node update endpoint.
- Added tests to ensure the correct behavior of the new feature and its integration with existing functionality.

backend/tests/PnvPanel.Domain.Tests/Nodes/NodeTests.cs

@@ -97,6 +97,19 @@ public class NodeTests
         Assert.True(node.IsEnabled);
     }
 
+    [Fact]
+    public void SetNotifyOnStatusChange_DefaultsFalse_AndCanBeToggled()
+    {
+        var node = Node.Register("Node", new Uri("https://example.com"), Credentials, null);
+        Assert.False(node.NotifyOnStatusChange);
+
+        node.SetNotifyOnStatusChange(true);
+        Assert.True(node.NotifyOnStatusChange);
+
+        node.SetNotifyOnStatusChange(false);
+        Assert.False(node.NotifyOnStatusChange);
+    }
+
     [Fact]
     public void UpdateStatus_SetsStatus()
     {