feat(cli): add English/Chinese i18n and refresh README

[LIghtJUNction]

Changes

• Extract 112 CLI user-facing messages into English and Simplified Chinese catalogs, with --lang, LMM_LANG, and system-locale detection.
• Translate help, catalog details, status/doctor/setup reports, OAuth and restoration messages; preserve machine-readable JSON keys and status codes.
• Refresh the English README, add Chinese README and bilingual usage guides.
• Add locale checks, CLI regression tests, and GitHub Actions checks.

Validation

• Translation catalog consistency, placeholders and source references: passed.
• Python i18n-checker tests: 7 passed.
• git diff --check and patch application verification: passed.
• Rust build, cargo test, formatting and clippy: not executed locally (Rust toolchain unavailable in the original workspace). CI must pass before merge.

Notes

• This is an i18n and documentation update, not a new integration adapter or a release.
• Some Clap-generated parameter-validation details are still in English; see docs/i18n.md.
• No production deployment or crate publication.