Refactor application to remove Windows Forms dependencies and transition to Avalonia UI

- Deleted MainWindow.xaml.cs, which contained the WPF implementation of the main window.
- Updated Program.cs to remove Windows Forms initialization and support only Avalonia UI.
- Removed Windows Forms specific code from ViewModelBase, including control marshalling logic.

imagecatalog/ViewModelBase.cs

@@ -6,18 +6,12 @@ using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
-#if WINDOWS
-using System.Windows.Forms;
-#endif
 
 namespace ImageCatalog_2
 {
     public class ViewModelBase : INotifyPropertyChanged
     {
         private readonly SynchronizationContext? _synchronizationContext;
-#if WINDOWS
-        private Control? _control;
-#endif
 
         protected ViewModelBase()
         {
@@ -25,19 +19,8 @@ namespace ImageCatalog_2
             _synchronizationContext = SynchronizationContext.Current;
         }
 
-        /// <summary>
-        /// Set a Control to use for thread marshalling in WinForms applications.
-        /// This is required for proper cross-thread handling with data binding.
-        /// </summary>
-#if WINDOWS
-        public void SetControl(Control control)
-        {
-            _control = control;
-        }
-#endif
-
         public event PropertyChangedEventHandler? PropertyChanged;
-        
+
         // This method is called by the Set accessor of each property.
         // The CallerMemberName attribute that is applied to the optional propertyName
         // parameter causes the property name of the caller to be substituted as an argument.
@@ -46,22 +29,6 @@ namespace ImageCatalog_2
             if (PropertyChanged == null)
                 return;
 
-#if WINDOWS
-            // If we have a Control reference (WinForms), use Control.Invoke for proper marshalling
-            if (_control != null)
-            {
-                if (_control.InvokeRequired)
-                {
-                    _control.Invoke(() => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)));
-                }
-                else
-                {
-                    PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
-                }
-            }
-            // Fallback to SynchronizationContext if available
-            else
-#endif
             if (_synchronizationContext != null && SynchronizationContext.Current != _synchronizationContext)
             {
                 // We're on a different thread, marshal to the UI thread