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 WPF/ViewModels/SettingsModel.cs

@@ -5,9 +5,26 @@ namespace TV_Player.ViewModels
 {
     public static class SettingsModel
     {
-        private static readonly string AppDataFolder = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData), "TVPlayer");
+        private static readonly string AppDataFolder = Path.Combine(GetWritableAppDataFolder(), "TVPlayer");
         private static readonly string SettingsFilePath = Path.Combine(AppDataFolder, "settings.json");
 
+        private static string GetWritableAppDataFolder()
+        {
+            var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+            if (!string.IsNullOrWhiteSpace(localAppData))
+            {
+                return localAppData;
+            }
+
+            var appData = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
+            if (!string.IsNullOrWhiteSpace(appData))
+            {
+                return appData;
+            }
+
+            return AppContext.BaseDirectory;
+        }
+
         public static Dictionary<string,string> Playlists { get; set; }
         public static bool StartFullScreen { get; set; } 
         public static bool StartFromLastScreen { get; set; }