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/rustdesk/rendezvous.rs

@@ -31,10 +31,6 @@ const MIN_REG_TIMEOUT_MS: u64 = 3_000;
 /// Maximum registration timeout
 const MAX_REG_TIMEOUT_MS: u64 = 30_000;
 
-/// Connection timeout
-#[allow(dead_code)]
-const CONNECT_TIMEOUT_MS: u64 = 18_000;
-
 /// Timer interval for checking registration status
 const TIMER_INTERVAL_MS: u64 = 300;
 
@@ -682,7 +678,6 @@ impl AddrMangle {
     }
 
     /// Decode bytes to SocketAddr using RustDesk's mangle algorithm
-    #[allow(dead_code)]
     pub fn decode(bytes: &[u8]) -> Option<SocketAddr> {
         use std::convert::TryInto;
         use std::net::{Ipv4Addr, Ipv6Addr, SocketAddrV4};