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/TelnetWindow.axaml

@@ -1,6 +1,7 @@
 <local:RefreshableWindow xmlns="https://github.com/avaloniaui"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:local="using:Nonemm.App.Windows"
+        xmlns:theming="using:Nonemm.App.Theming"
         x:Class="Nonemm.App.Windows.TelnetWindow"
         Title="Telnet" Width="760" Height="520">
   <Window.Styles>
@@ -32,7 +33,7 @@
             <TextBox Name="CommandBox" PlaceholderText="command to the node" KeyDown="OnCommandKey" />
           </DockPanel>
         </StackPanel>
-        <ListBox Name="Traffic" FontFamily="monospace" FontSize="12" Margin="8,0"
+        <ListBox Name="Traffic" FontFamily="{x:Static theming:Fonts.Mono}" FontSize="12" Margin="8,0"
                  DoubleTapped="OnJumpToSpot">
           <ListBox.ContextMenu>
             <ContextMenu>