refactor: 清理死代码和优化日志级别

- 删除未使用的函数和常量
  - create_public_key_message (rustdesk/connection)
  - decode_audio_packet, AudioPacketHeader (web/audio_ws)
  - io_error_to_hid_error, close_device, close_all_devices (hid)
  - shutdown_rx (rustdesk/mod)
  - CONNECT_TIMEOUT_MS, RESP_ERR_SEND_FAILED

- 调整日志级别
  - Session lagged: warn -> debug
  - 移除 H264 NAL trace 日志
  - 移除 Frame distribution lagged trace 日志
  - 移除 absolute mouse report trace 日志

- 优化 broadcast channel 缓冲区大小 8 -> 16

- 修复条件编译
  - static_files.rs: 添加 debug_assertions 条件

src/hid/websocket.rs

@@ -28,8 +28,6 @@ use crate::utils::LogThrottler;
 const RESP_OK: u8 = 0x00;
 const RESP_ERR_HID_UNAVAILABLE: u8 = 0x01;
 const RESP_ERR_INVALID_MESSAGE: u8 = 0x02;
-#[allow(dead_code)]
-const RESP_ERR_SEND_FAILED: u8 = 0x03;
 
 /// WebSocket HID upgrade handler
 pub async fn ws_hid_handler(ws: WebSocketUpgrade, State(state): State<Arc<AppState>>) -> Response {