Fix: 修复日志系统权限问题，支持容器环境

Add client IP logging functionality: Implement `get_client_ip` to retrieve real client IP addresses, enhancing request logging in `before_request`. Update Dockerfile to use Gunicorn with configuration for accurate IP logging. Update VSCode completion for new function.

Refactor application to Flask: enhance structure with RESTful API, static file support, and logging. Update Dockerfile for production with Gunicorn and health checks. Expand requirements for Flask and OpenSearch integration.

Update README.md with application title, features, usage guide, and technology stack for the interactive English learning app.