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/atx/led.rs

@@ -55,7 +55,10 @@ impl LedSensor {
             .map_err(|e| AppError::Internal(format!("LED GPIO chip failed: {}", e)))?;
 
         let line = chip.get_line(self.config.gpio_pin).map_err(|e| {
-            AppError::Internal(format!("LED GPIO line {} failed: {}", self.config.gpio_pin, e))
+            AppError::Internal(format!(
+                "LED GPIO line {} failed: {}",
+                self.config.gpio_pin, e
+            ))
         })?;
 
         let handle = line