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

@@ -0,0 +1,38 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        x:Class="TV_Player.AvaloniaApp.MainWindow"
+        mc:Ignorable="d"
+        Width="1400"
+        Height="860"
+        MinWidth="980"
+        MinHeight="640"
+        Title="TV Player"
+        WindowState="{Binding CurrentWindowState}"
+        Background="#0B1220">
+  <Grid RowDefinitions="Auto,*">
+    <Border IsVisible="{Binding IsTopPanelVisible}"
+            Background="#AA111827"
+            BorderBrush="#33FFFFFF"
+            BorderThickness="0,0,0,1"
+            Padding="20,14">
+      <Grid ColumnDefinitions="Auto,Auto,*,Auto,Auto">
+        <Button Content="Settings" Command="{Binding SettingsCommand}" MinWidth="92" Margin="0,0,12,0" />
+        <Button Grid.Column="1" Content="Back" Command="{Binding BackCommand}" MinWidth="92" Margin="0,0,12,0" />
+        <TextBlock Grid.Column="2"
+                   Text="{Binding TopPanelTitle}"
+                   FontSize="26"
+                   FontWeight="SemiBold"
+                   VerticalAlignment="Center"
+                   HorizontalAlignment="Center" />
+        <Button Grid.Column="3" Content="Fullscreen" Command="{Binding FullscreenCommand}" MinWidth="110" Margin="0,0,12,0" />
+        <Button Grid.Column="4" Content="Close" Command="{Binding CloseAppCommand}" MinWidth="92" />
+      </Grid>
+    </Border>
+
+    <Border Grid.Row="1" Padding="20">
+      <ContentControl Content="{Binding CurrentViewModel}" />
+    </Border>
+  </Grid>
+</Window>