[feat] WPF 회원관리 애플리케이션 구현

- .NET 8.0 WPF 프로젝트 생성
- MVVM 패턴 적용 (CommunityToolkit.Mvvm)
- 의존성 주입 구현 (Microsoft.Extensions.DependencyInjection)
- 로그인/회원관리/회원등록 화면 구현
- 테마 전환 기능 (Dark/Light)
- 다국어 지원 (한국어/영어)
- 세련된 로그인 UI 디자인
- CLAUDE.md 및 History.md 문서화

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/WPFBeginner/Views/MainWindow.xaml.cs

@@ -0,0 +1,27 @@
+using System.Windows;
+using System.Windows.Input;
+using WPFBeginner.ViewModels;
+
+namespace WPFBeginner.Views;
+
+public partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+        DataContext = App.GetService<MainViewModel>();
+    }
+
+    private void SettingsButton_Click(object sender, RoutedEventArgs e)
+    {
+        SettingsPopup.IsOpen = !SettingsPopup.IsOpen;
+    }
+
+    private void SearchTextBox_KeyDown(object sender, KeyEventArgs e)
+    {
+        if (e.Key == Key.Enter && DataContext is MainViewModel viewModel)
+        {
+            viewModel.SearchCommand.Execute(null);
+        }
+    }
+}