chore: 更新默认信令服务器地址为 wss://www.ttstd.com/signal

webrtc_controller_flutter/lib/config/ice_servers.dart

@@ -20,7 +20,7 @@ const List<Map<String, dynamic>> kIceServers = [
 ];
 
 /// 信令 WebSocket 默认地址。
-const String kDefaultSignalServer = 'ws://175.178.213.60:8088/ws/signal';
+const String kDefaultSignalServer = 'wss://www.ttstd.com/signal';
 
 /// DataChannel 标签，控制端与被控端需一致。
 const String kDataChannelLabel = 'control_channel';