* docs: add Simplified Chinese translation (README.zh.md)
* docs: sync README.zh.md with current English README
Address review findings:
- Fix stale Railway URLs (railway.app -> railway.com, /template/ -> /deploy/)
- Add missing Resumable Streams section
- Add missing sub-features (Agent Marketplace, Collaborative Sharing, Jina
Reranking, prompt sharing, Helicone provider)
- Update multilingual UI language list from 18 to 30+ languages
- Replace outdated "ChatGPT clone" platform description with current messaging
- Remove stale video embed no longer in English README
- Remove non-standard bold wrappers on links
- Fix trailing whitespace
- Add sync header with date and commit SHA
---------
Co-authored-by: Danny Avila <danny@librechat.ai>
