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/StreamConfig.cs

@@ -0,0 +1,35 @@
+namespace ytLive.Models;
+
+public enum StreamStatus
+{
+    Offline,
+    Connecting,
+    Streaming,
+    Error
+}
+
+public class StreamConfig
+{
+    public string Title { get; set; } = string.Empty;
+    public string Description { get; set; } = string.Empty;
+    public string StreamKey { get; set; } = string.Empty;
+    public string IngestUrl { get; set; } = "rtmp://a.rtmp.youtube.com/live2";
+    public bool IsLowLatency { get; set; } = true;
+    public int TargetBitrate { get; set; } = 6000;
+    public int TargetFps { get; set; } = 60;
+    public string Resolution { get; set; } = "1920x1080";
+}
+
+public class StreamHealth
+{
+    public StreamStatus Status { get; set; }
+    public double CurrentBitrate { get; set; }
+    public int DroppedFrames { get; set; }
+    public double FPS { get; set; }
+    public TimeSpan StreamDuration { get; set; }
+    public string? LastError { get; set; }
+
+    // YouTube-specific
+    public string? HealthStatus { get; set; }  // "good", "bad", "ok"
+    public string? HealthMessage { get; set; }
+}