feat(webrtc): 添加公共ICE服务器支持和优化HID延迟

- 重构ICE配置：将TURN配置改为统一的ICE配置，支持STUN和多TURN URL
- 添加公共ICE服务器：类似RustDesk，用户留空时使用编译时配置的公共服务器
- 优化DataChannel HID消息：使用tokio::spawn立即处理，避免依赖webrtc-rs轮询
- 添加WebRTCReady事件：客户端等待此事件后再建立连接
- 初始化时启动音频流，确保WebRTC可订阅
- 移除多余的trace/debug日志减少开销
- 更新前端配置界面支持公共ICE服务器显示

secrets.toml.example

@@ -0,0 +1,23 @@
+# One-KVM Secrets Configuration
+# Copy this file to secrets.toml and fill in your values
+# secrets.toml is ignored by git and will be read at compile time
+
+[rustdesk]
+# Public RustDesk ID server (hbbs) for users who leave the field empty
+public_server = ""
+# Public key for the RustDesk server (displayed to users)
+public_key = ""
+# Relay server authentication key (if relay server uses -k option)
+relay_key = ""
+
+[ice]
+# Public ICE servers for WebRTC NAT traversal
+# These servers are used when users enable "Use public ICE servers" option
+# STUN server URL (for NAT type detection)
+stun_server = ""
+# TURN server URLs (for relay when direct connection fails)
+# Supports multiple URLs separated by comma
+turn_urls = ""
+# TURN authentication credentials
+turn_username = ""
+turn_password = ""