feat: simplify page navigation display

Updated the `TextBlock` in the navigation `Button` to present the selected page index and total pages in a more concise format ("X / Y") instead of the previous verbose format ("At X of Y Pages"). This change improves clarity and reduces visual clutter in the user interface.

SketchNow/Views/PageNavigationView.xaml

@@ -28,7 +28,7 @@
     <Button Width="200"
             Height="48"
             Style="{StaticResource MaterialDesignFlatButton}">
-      <TextBlock VerticalAlignment="Center"><Run Text="At " /><Run Text=" " /><Run Text="{Binding CanvasPages.SelectedIndex, Mode=OneWay}" /><Run Text=" " /><Run Text="of " /><Run Text=" " /><Run Text="{Binding CanvasPages.Pages.Count, ConverterParameter=-1, Converter={StaticResource MathAddConverter}, Mode=OneWay}" /><Run Text=" " /><Run Text=" Pages" /></TextBlock>
+      <TextBlock VerticalAlignment="Center"><Run Text="{Binding CanvasPages.SelectedIndex, Mode=OneWay}" /><Run Text=" / " /><Run Text="{Binding CanvasPages.Pages.Count, ConverterParameter=-1, Converter={StaticResource MathAddConverter}, Mode=OneWay}" /></TextBlock>
     </Button>
     <Button Height="48"
             Command="{Binding CanvasPages.AddPageCommand}"