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/hid/types.rs

@@ -341,12 +341,7 @@ pub struct MouseReport {
 impl MouseReport {
     /// Convert to bytes for USB HID (relative mouse)
     pub fn to_bytes_relative(&self) -> [u8; 4] {
-        [
-            self.buttons,
-            self.x as u8,
-            self.y as u8,
-            self.wheel as u8,
-        ]
+        [self.buttons, self.x as u8, self.y as u8, self.wheel as u8]
     }
 
     /// Convert to bytes for USB HID (absolute mouse)