Create English README with Chinese version appended

[Copilot]

Summary

This PR transforms the README.md into a bilingual document with English as the primary language and Chinese as an appendix, making the project accessible to the global developer community while maintaining full support for Chinese users.

Changes

📘 English Version (Primary Documentation)

• Complete professional English translation of all 12 major sections
• Covers Quick Start, RAG System Setup, Technical Features, Usage Guide, and more
• All technical commands, code blocks, and file paths preserved unchanged
• Maintains the project's emoji-rich, modern documentation style

📕 Chinese Version (Appendix)

• Complete original Chinese documentation preserved
• Added clear separator with --- and # 中文版本 / Chinese Version header
• Identical structure and content to English version
• All sections mirrored for consistency

🔧 Documentation Improvements

Based on code review feedback, several accuracy improvements were made:

1. MongoDB Requirements: Added minimum version requirement (>= 4.4) to system requirements
2. API Configuration: Corrected environment variable documentation to use DASHSCOPE_API_KEY (Qwen/DashScope) instead of OpenAI API key
3. Server Port: Fixed documented port from 8080 to 3001 to match actual implementation
4. API Key Documentation: Added direct link to DashScope API registration: https://dashscope.aliyun.com/
5. Repository Links: Updated all GitHub links from placeholder to actual repository URL: LQ458/lesson-plan-generator

Structure

README.md (791 lines)
├── English Version (Lines 1-391)
│   ├── 📚 Project Title & Description
│   ├── 🚀 Quick Start & Installation
│   ├── 🧠 RAG System Setup
│   ├── 🏃‍♂️ Running the Project
│   ├── 📚 Educational Materials Data
│   ├── 🎯 Technical Features
│   ├── 📖 Usage Guide
│   ├── 📁 Project Structure
│   ├── 🛠️ Development Tools
│   ├── 🔑 Environment Configuration
│   ├── 📖 Technology Stack
│   └── 🤝 Contributing & License
├── --- (Separator)
└── Chinese Version (Lines 392-791)
    └── [Complete Chinese translation with identical structure]

Benefits

• Global Accessibility: English documentation enables international developers to contribute and use the project
• Bilingual Support: Chinese users retain full access to documentation in their native language
• Accurate Configuration: Environment setup now matches actual implementation requirements
• Professional Quality: Native-level English translation with technical accuracy preserved
• SEO Improvement: English content improves discoverability in global search results

Testing

• ✅ Markdown syntax validated (88 code blocks, 115 headings)
• ✅ All sections present in both languages
• ✅ Code blocks and commands identical across versions
• ✅ Links verified and updated to correct repository
• ✅ Environment configuration matches actual implementation

This change makes TeachAI more accessible to the global developer community while maintaining excellent support for Chinese users! 🌍🚀

Original prompt

write an English md for this project based on the original md and make it the main md, attach chinese version at the end.

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