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/ch9329.rs

@@ -449,29 +449,6 @@ impl Ch9329Backend {
         self.port.lock().is_some()
     }
 
-    /// Convert I/O error to HidError with appropriate error code
-    #[allow(dead_code)]
-    fn io_error_to_hid_error(e: std::io::Error, operation: &str) -> AppError {
-        let error_code = match e.kind() {
-            std::io::ErrorKind::NotFound => "port_not_found",
-            std::io::ErrorKind::PermissionDenied => "permission_denied",
-            std::io::ErrorKind::TimedOut => "timeout",
-            std::io::ErrorKind::BrokenPipe => "broken_pipe",
-            _ => match e.raw_os_error() {
-                Some(6) => "enxio",      // ENXIO - no such device
-                Some(19) => "enodev",    // ENODEV - no such device
-                Some(5) => "eio",        // EIO - I/O error
-                _ => "serial_error",
-            },
-        };
-
-        AppError::HidError {
-            backend: "ch9329".to_string(),
-            reason: format!("{}: {}", operation, e),
-            error_code: error_code.to_string(),
-        }
-    }
-
     /// Convert serialport error to HidError
     fn serial_error_to_hid_error(e: serialport::Error, operation: &str) -> AppError {
         let error_code = match e.kind() {