docs: update README files with enhanced features and installation instructions

- Revised the English and Chinese README files to reflect the latest features and capabilities of Claude Code Hub.
- Improved descriptions of core functionalities, including intelligent load balancing, multi-provider management, and automated OpenAPI documentation.
- Updated installation instructions to clarify environment requirements and configuration steps.
- Enhanced the bilingual language switcher for better accessibility.

This update aims to provide clearer guidance and showcase the platform's capabilities more effectively.