- Dart: Add explicit Future<void> return type to send() method
- Dart: Improve onDisconnected() logic with proper isAlive handling and heartbeat response
- Go: Introduce baseClient generic base class for shared client logic
- Go: Refactor TcpClient and WsClient to embed baseClient instead of embedding Communicator
- Remove duplicate heartbeat and disconnect handling code across client implementations
- Clean up unused imports (time package)
