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/video/video_session.rs

@@ -234,10 +234,7 @@ impl VideoSessionManager {
         let mut sessions = self.sessions.write().await;
         sessions.insert(session_id.clone(), session);
 
-        info!(
-            "Video session created: {} (codec: {})",
-            session_id, codec
-        );
+        info!("Video session created: {} (codec: {})", session_id, codec);
 
         Ok(session_id)
     }
@@ -428,8 +425,7 @@ impl VideoSessionManager {
             sessions
                 .iter()
                 .filter(|(_, s)| {
-                    (s.state == VideoSessionState::Paused
-                        || s.state == VideoSessionState::Created)
+                    (s.state == VideoSessionState::Paused || s.state == VideoSessionState::Created)
                         && now.duration_since(s.last_activity) > timeout
                 })
                 .map(|(id, _)| id.clone())