Set canvas state to idle after adding new connection

When a new connection is added to the view model, the canvas state is now set to idle. This change helps to ensure that the canvas is properly reset and ready for the next interaction.

ScenariumEditor.NET/ScenariumEditor.NET/MainWindow.xaml.cs

@@ -106,6 +106,7 @@ private void GraphCanvasBg_OnButtonDown(object sender, MouseButtonEventArgs e) {
                 if (_nearestPin != null) {
                     _viewModel.Connections.Add(new Connection(_activePin, _nearestPin));
                     CancelNewConnection();
+                    _canvasState = CanvasState.Idle;
                 }
 
                 return;