DeliveryAncmtAdminWindow: Focus MgNrInput when creating new ancmt

Elwig/Windows/DeliveryAncmtAdminWindow.xaml.cs

@@ -276,6 +276,9 @@ namespace Elwig.Windows {
             InitInputs();
             ViewModel.MgNr = mgnr;
             ViewModel.EnableSearchInputs = false;
+
+            MgNrInput.Focus();
+            MgNrInput.SelectAll();
         }
 
         protected override void ShortcutEdit() {