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

libs/ventoy-img-rs/src/image.rs

@@ -22,7 +22,11 @@ impl VentoyImage {
         let size = parse_size(size_str)?;
         let layout = PartitionLayout::calculate(size)?;
 
-        println!("[INFO] Creating {}MB image: {}", size / (1024 * 1024), path.display());
+        println!(
+            "[INFO] Creating {}MB image: {}",
+            size / (1024 * 1024),
+            path.display()
+        );
 
         // Create sparse file
         let mut file = File::create(path)?;
@@ -247,7 +251,11 @@ impl VentoyImage {
     ///
     /// This is the preferred method for large files as it doesn't load
     /// the entire file into memory.
-    pub fn read_file_to_writer<W: std::io::Write>(&self, path: &str, writer: &mut W) -> Result<u64> {
+    pub fn read_file_to_writer<W: std::io::Write>(
+        &self,
+        path: &str,
+        writer: &mut W,
+    ) -> Result<u64> {
         let mut fs = ExfatFs::open(&self.path, &self.layout)?;
         fs.read_file_path_to_writer(path, writer)
     }