Fix title bar icon missing in single-file published builds

The title bar Image used Source="ms-appx:///Assets/Square44x44Logo.scale-200.png".
That resolves fine in a normal build (Assets/ and AmiReel.pri sit next to the exe),
but a single-file self-contained publish (IncludeAllContentForSelfExtract=true)
bundles Content items into the exe in a way ms-appx:// can no longer resolve at
runtime, leaving the title bar icon blank — reproduced with the actual
publish-win-x64.ps1 output, confirmed fixed the same way.

Load the icon from a plain embedded resource instead (same mechanism already
used for ffmpeg.exe/ffprobe.exe): the PNG is embedded via
<EmbeddedResource LogicalName="AmiReel.Assets.TitleBarIcon.png">, and
MainWindow loads it at startup via GetManifestResourceStream + BitmapImage.
SetSourceAsync. This bypasses the ms-appx/MRT resource pipeline entirely, so
it behaves identically in dotnet build, dotnet run, and a single-file publish.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

MainWindow.xaml

@@ -16,7 +16,7 @@
 
         <Grid x:Name="AppTitleBar" Grid.Row="0" Height="44" Background="{ThemeResource PanelBrush}">
             <StackPanel Orientation="Horizontal" Spacing="10" VerticalAlignment="Center" Margin="14,0,0,0">
-                <Image Source="ms-appx:///Assets/Square44x44Logo.scale-200.png"
+                <Image x:Name="TitleBarIcon"
                        Width="20"
                        Height="20"
                        Stretch="Uniform" />