feat(video): 事务化切换与前端统一编排，增强视频输入格式支持

- 后端：切换事务+transition_id，/stream/mode 返回 switching/transition_id 与实际 codec

- 事件：新增 mode_switching/mode_ready，config/webrtc_ready/mode_changed 关联事务

- 编码/格式：扩展 NV21/NV16/NV24/RGB/BGR 输入与转换链路，RKMPP direct input 优化

- 前端：useVideoSession 统一切换，失败回退真实切回 MJPEG，菜单格式同步修复

- 清理：useVideoStream 降级为 MJPEG-only

src/msd/mod.rs

@@ -15,19 +15,19 @@
 //! ```
 
 pub mod controller;
-pub mod ventoy_drive;
 pub mod image;
 pub mod monitor;
 pub mod types;
+pub mod ventoy_drive;
 
 pub use controller::MsdController;
-pub use ventoy_drive::VentoyDrive;
 pub use image::ImageManager;
 pub use monitor::{MsdHealthMonitor, MsdHealthStatus, MsdMonitorConfig};
 pub use types::{
     DownloadProgress, DownloadStatus, DriveFile, DriveInfo, DriveInitRequest, ImageDownloadRequest,
     ImageInfo, MsdConnectRequest, MsdMode, MsdState,
 };
+pub use ventoy_drive::VentoyDrive;
 
 // Re-export from otg module for backward compatibility
 pub use crate::otg::{MsdFunction, MsdLunConfig};