docs: multilingual READMEs + WeCom QR

[XYAIStudio]

Summary

Describe the user-visible or operator-visible outcome.

Security and data impact

Describe authentication, authorization, tenant isolation, secrets, migrations, and stored-data effects. Write “None” only after checking each item.

Verification

List the exact commands and manual paths you ran.

Checklist

• No credentials, customer data, runtime databases, uploads, logs, or build artifacts are included.
• Tests cover changed behavior and relevant failure paths.
• User-visible changes include both zh-CN and en copy; changed routes were checked in both languages.
• New or changed AI flows have verified output language behavior where applicable.
• Configuration and documentation are updated.
• npm run verify:open-source passes.
• Every commit has a DCO Signed-off-by line.
• A maintainer has verified the applicable ICLA/CCLA and applied cla-signed.