feat(hid): 添加 Consumer Control 多媒体按键和多平台键盘布局

- 新增 Consumer Control HID 支持（播放/暂停、音量控制等）
- 虚拟键盘支持 Windows/Mac/Android 三种布局切换
- 移除键盘 LED 反馈以节省 USB 端点（从 2 减至 1）
- InfoBar 优化：按键名称友好显示，移除未实现的 Num/Scroll 指示器
- 更新 HID 模块文档

src/hid/backend.rs

@@ -3,7 +3,7 @@
 use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 
-use super::types::{KeyboardEvent, MouseEvent};
+use super::types::{ConsumerEvent, KeyboardEvent, MouseEvent};
 use crate::error::Result;
 
 /// Default CH9329 baud rate
@@ -94,6 +94,14 @@ pub trait HidBackend: Send + Sync {
     /// Send a mouse event
     async fn send_mouse(&self, event: MouseEvent) -> Result<()>;
 
+    /// Send a consumer control event (multimedia keys)
+    /// Default implementation returns an error (not supported)
+    async fn send_consumer(&self, _event: ConsumerEvent) -> Result<()> {
+        Err(crate::error::AppError::BadRequest(
+            "Consumer control not supported by this backend".to_string(),
+        ))
+    }
+
     /// Reset all inputs (release all keys/buttons)
     async fn reset(&self) -> Result<()>;