fix: resolve frontend and backend default port conflict

[AlabasterStone]

• 修改readme中的typo
• 前后端端口一致
• openai兼容的api没有deepseek模型

[Copilot]

Pull request overview

This pull request addresses three key issues: fixing a repository URL typo, resolving frontend-backend port conflicts, and updating the default LLM model for OpenAI API compatibility.

Changes:

• Fixed repository clone URL from placeholder "your-org" to actual "OpenDCAI" organization
• Updated backend server port from 8000 to 8211 in documentation to match actual deployment configuration
• Changed default LLM model from deepseek-v3.2 to gpt-4o in frontend_zh for OpenAI-compatible API support
• Added frontend_en and frontend_zh build artifacts to .gitignore

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Updated repository URL and backend port from 8000 to 8211 in startup instructions and health check URLs
README_EN.md	Updated repository URL and backend port from 8000 to 8211 in startup instructions and API documentation URLs
frontend_en/INTEGRATION_GUIDE.md	Updated backend proxy configuration from port 8210 to 8211
frontend_zh/src/pages/NotebookView.tsx	Changed default LLM model from deepseek-v3.2 to gpt-4o for all studio tools (ppt, mindmap, drawio, flashcard, quiz, podcast, video)
.gitignore	Added node_modules, dist, build, and .vite directories for frontend_en and frontend_zh

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