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/state.rs

@@ -5,7 +5,10 @@ use crate::atx::AtxController;
 use crate::audio::AudioController;
 use crate::auth::{SessionStore, UserStore};
 use crate::config::ConfigStore;
-use crate::events::{AtxDeviceInfo, AudioDeviceInfo, EventBus, HidDeviceInfo, MsdDeviceInfo, SystemEvent, VideoDeviceInfo};
+use crate::events::{
+    AtxDeviceInfo, AudioDeviceInfo, EventBus, HidDeviceInfo, MsdDeviceInfo, SystemEvent,
+    VideoDeviceInfo,
+};
 use crate::extensions::ExtensionManager;
 use crate::hid::HidController;
 use crate::msd::MsdController;