Give the desktop head the mark the phone has carried all along

The window had no icon and the executable had no icon, so Windows drew its
generic one in the taskbar, in alt-tab and in Explorer, next to an application
that draws its own titlebar precisely so that nothing about it looks borrowed.

The geometry is the launcher vector's, mapped so the middle 72 of its 108-unit
viewport fills the canvas: that 72 is what an adaptive icon actually shows, and
rendering the full 108 would draw the mark at 39% of the width. Nine sizes,
because Windows asks for several and downsamples unkindly when one is missing,
and a floor of one pixel on the strokes so 16px is a mark rather than a smudge.

Windows takes an .ico and nothing else, so the raster the phone does not need
exists here. dodossh-icon.ps1 sits beside it and draws it from those same
numbers, so the two heads still have one geometry between them.

src/DodoSSH.Client.App/DodoSSH.Client.App.csproj

@@ -5,6 +5,14 @@
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
 
+    <!--
+      The icon on the executable itself — what Explorer, the Start menu and a pinned taskbar button
+      draw, all of which read it from the PE resource and never start the process. Window.Icon in
+      MainWindow.axaml is a separate thing that only exists once the application is running; both are
+      needed, and both point at this file.
+    -->
+    <ApplicationIcon>Assets/dodossh.ico</ApplicationIcon>
+
     <!--
       False here, unlike every server project. The root Directory.Build.props sets it true because
       the API is container-hosted, UTC-only and has no business formatting anything for a human.
@@ -15,6 +23,14 @@
     <InvariantGlobalization>false</InvariantGlobalization>
   </PropertyGroup>
 
+  <ItemGroup>
+    <!--
+      Named rather than globbed as Assets/**, because the folder also holds the script that draws the
+      icon and a build has no reason to carry a copy of it around inside the binary.
+    -->
+    <AvaloniaResource Include="Assets/dodossh.ico" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Avalonia" />
     <PackageReference Include="Avalonia.Desktop" />