docs: clarify CORS security recommendations

[chenjiahan]

Summary

Update the CORS configuration documentation and type definitions to improve clarity and security recommendations.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR updates the CORS configuration documentation and type definitions to clarify the security implications when enabling CORS with default options.

• Clarifies that enabling CORS with default options allows all origins, which is not recommended.
• Retains existing functionality with a clearer explanation in the documentation.

Files not reviewed (2)

• website/docs/en/config/server/cors.mdx: Language not supported
• website/docs/zh/config/server/cors.mdx: Language not supported