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/encoder.rs

@@ -137,9 +137,8 @@ impl OpusEncoder {
         let channels = config.to_audiopus_channels();
         let application = config.to_audiopus_application();
 
-        let mut encoder = Encoder::new(sample_rate, channels, application).map_err(|e| {
-            AppError::AudioError(format!("Failed to create Opus encoder: {:?}", e))
-        })?;
+        let mut encoder = Encoder::new(sample_rate, channels, application)
+            .map_err(|e| AppError::AudioError(format!("Failed to create Opus encoder: {:?}", e)))?;
 
         // Configure encoder
         encoder