Initial scaffold: ytLive C# WPF project

- MVVM architecture (Models, ViewModels, Views, Services, Helpers)
- Models: Scene, Source, StreamConfig, StreamHealth, YouTubeChannel, ChatMessage
- Services: YouTubeAuthService (OAuth2), YouTubeStreamService (broadcasts/stream health),
  YouTubeChatService (live chat polling)
- ViewModels: MainViewModel with scene management, stream controls, chat
- MainWindow with dark theme: scene/source panel, preview area, chat panel, status bar
- Version roadmap: v0.1 (scenes, RTMP, OAuth2, chat, health) -> 1.0

Models/Source.cs

@@ -0,0 +1,35 @@
+namespace ytLive.Models;
+
+public enum SourceType
+{
+    DisplayCapture,
+    WindowCapture,
+    Webcam,
+    Image,
+    TextOverlay
+}
+
+public class Source
+{
+    public string Id { get; init; } = Guid.NewGuid().ToString();
+    public string Name { get; set; } = string.Empty;
+    public SourceType Type { get; set; }
+    public bool IsEnabled { get; set; } = true;
+
+    // Display/Window capture
+    public int? MonitorIndex { get; set; }
+    public IntPtr? WindowHandle { get; set; }
+
+    // Webcam
+    public string? DeviceId { get; set; }
+
+    // Image
+    public string? FilePath { get; set; }
+
+    // Position/transform
+    public double X { get; set; }
+    public double Y { get; set; }
+    public double Width { get; set; }
+    public double Height { get; set; }
+    public double Opacity { get; set; } = 1.0;
+}