Release v4.0.0: 全新架构重写，支持Header预配置和多数据库管理，简化工具和提升性能。移除旧的连接管理器，优化代码结构，增强用户体验。

v4.0.5: Fix connection closed error with connection pool

- Replace single connection with connection pool
- Add keep-alive mechanism to prevent timeout
- Add auto-reconnect functionality
- Support concurrent queries
- Fix 'Can't add new command when connection is in closed state' error