feat: Implement Playlists and Programs Management

- Added PlaylistsGroupViewModel to manage playlists and selection.
- Introduced ProgramsGroupViewModel for handling program groups and subscriptions.
- Created ProgramsListViewModel to manage individual program listings.
- Developed SettingsViewModel for user settings including playlist management.
- Implemented TVPlayerViewModel as the main view model coordinating screens and data.
- Added PlayerView for video playback with LibVLC integration.
- Created XAML views for PlaylistsGroup, ProgramsGroup, ProgramsList, and Settings.
- Added sample M3U playlist for testing.
- Documented WPF build instructions and project structure in WPF-BUILD.md.
- Configured global.json for .NET SDK versioning.

TV Player Avalonia/MainWindow.axaml.cs

@@ -0,0 +1,29 @@
+using Avalonia.Controls;
+using Avalonia.Input;
+using TV_Player.AvaloniaApp.ViewModels;
+
+namespace TV_Player.AvaloniaApp;
+
+public partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+        KeyDown += OnKeyDown;
+    }
+
+    private void OnKeyDown(object? sender, KeyEventArgs e)
+    {
+        if (DataContext is not MainWindowViewModel viewModel)
+            return;
+
+        if (e.Key == Key.Escape)
+        {
+            viewModel.OnCloseAppButtonClick();
+        }
+        else if (e.Key == Key.Back)
+        {
+            viewModel.TriggerBack();
+        }
+    }
+}