docs: bilingual README (en + zh-CN)

[Pigbibi]

Summary

Documentation-only change. Align README.md and README.zh-CN.md with the
QuantStrategyLab documentation style guide.

Why

The previous READMEs used internal architecture language, listed internal
documents, and diverged between English and Chinese.

Changes

• Rewrite the English README to the required section order (Status, What this
  is, What this is not, Quick start, Configuration, Repository layout,
  Contributing, Security, License).
• Add a matching Simplified Chinese README with the same sections, order,
  commands, links, and configuration names.
• Describe the input files and output contract plainly instead of internal
  architecture notes.

Testing

No code changed. Verified both files against the style-guide checklist and grep
list: no absolute home paths, non-placeholder buckets, personal subdomains,
40-character hex strings, status tables, dated audit titles, or process
narration. Confirmed the two files have the same sections in the same order.

Risk and rollback

Docs only. Revert the commit to roll back.

Breaking changes

none