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/web/static_files.rs

@@ -4,9 +4,10 @@ use axum::{
     routing::get,
     Router,
 };
+#[cfg(debug_assertions)]
 use std::path::PathBuf;
+#[cfg(debug_assertions)]
 use std::sync::OnceLock;
-use tracing;
 
 // Only embed assets in release mode
 #[cfg(not(debug_assertions))]
@@ -22,6 +23,7 @@ pub struct StaticAssets;
 /// Get the base directory for static files
 /// In debug mode: relative to executable directory
 /// In release mode: not used (embedded assets)
+#[cfg(debug_assertions)]
 fn get_static_base_dir() -> PathBuf {
     static BASE_DIR: OnceLock<PathBuf> = OnceLock::new();
     BASE_DIR.get_or_init(|| {