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/audio/streamer.rs

@@ -297,11 +297,8 @@ impl AudioStreamer {
             }
 
             // Receive PCM frame with timeout
-            let recv_result = tokio::time::timeout(
-                std::time::Duration::from_secs(2),
-                pcm_rx.recv(),
-            )
-            .await;
+            let recv_result =
+                tokio::time::timeout(std::time::Duration::from_secs(2), pcm_rx.recv()).await;
 
             match recv_result {
                 Ok(Ok(audio_frame)) => {