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.cs

@@ -2,9 +2,12 @@ using Microsoft.UI;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media.Imaging;
 using System;
 using System.IO;
+using System.Reflection;
 using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
 using Windows.Graphics;
 using Windows.UI;
 using WinRT.Interop;
@@ -36,6 +39,7 @@ public sealed partial class MainWindow : Window
             AppWindow.SetIcon(executablePath);
 
         SetDefaultSizeAndPosition();
+        LoadTitleBarIcon();
 
         // Navigate the root frame to the main page on startup.
         RootFrame.Navigate(typeof(MainPage));
@@ -43,6 +47,30 @@ public sealed partial class MainWindow : Window
         AppWindow.Closing += AppWindow_Closing;
     }
 
+    /// <summary>
+    /// Loads the title bar icon from an embedded resource instead of an "ms-appx:///Assets/..."
+    /// URI. A single-file self-contained publish bundles Content/Assets items into the exe in a
+    /// way the ms-appx resource pipeline can no longer resolve at runtime, leaving the title bar
+    /// blank; a plain embedded resource stream works the same in every publish mode.
+    /// </summary>
+    private async void LoadTitleBarIcon()
+    {
+        try
+        {
+            Assembly assembly = Assembly.GetExecutingAssembly();
+            using Stream? stream = assembly.GetManifestResourceStream("AmiReel.Assets.TitleBarIcon.png");
+            if (stream is null) return;
+
+            BitmapImage bitmap = new();
+            await bitmap.SetSourceAsync(stream.AsRandomAccessStream());
+            TitleBarIcon.Source = bitmap;
+        }
+        catch
+        {
+            // Non-critical: the title bar simply shows no icon if this fails.
+        }
+    }
+
     private void SetDefaultSizeAndPosition()
     {
         const int DefaultWidth = 1280;