Name a monospace font list instead of the generic monospace

The generic name only resolves through fontconfig, so on Windows the
windows fell back to the proportional default.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Nonemm.App/Windows/AvailableWindow.axaml.cs

@@ -1,3 +1,4 @@
+using Nonemm.App.Theming;
 using Avalonia.Controls;
 using Avalonia.Input;
 using Avalonia.Layout;
@@ -85,7 +86,7 @@ public sealed partial class AvailableWindow : RefreshableWindow
         TextBlock text = new()
         {
             Text = Label(station),
-            FontFamily = new FontFamily("monospace"),
+            FontFamily = Fonts.Mono,
             FontSize = 13,
             Foreground = Verdicts.Colour(station.Verdict),
             HorizontalAlignment = HorizontalAlignment.Left,