- rewrite the default README in natural GitHub-facing English, add a dedicated README.zh-CN.md companion, and align the deployment guide with the documented installer behavior
- add explicit installer language selection with bilingual prompts, summaries, generated install notes, and help output while keeping --lang available for scripted runs
- fix formatted installer messages so download and validation logs keep their interpolated values instead of dropping the target url or path
- copy apps/api/.env.example into the deployment .env first
- only override deployment-specific values such as image, ports, origin, and log level
- keep new example fields like TZ and cron settings in sync automatically
- rename user-facing deployment modes to 完整部署 and 仅后端部署
- simplify README and DEPLOYMENT wording for end users
- polish generated INSTALL-README guidance and upgrade steps
