docs: correct and clarify documentation

[ZingerLittleBee]

Summary

• correct factual inaccuracies across the English and Chinese documentation
• simplify wording and keep bilingual pages aligned
• add contract checks for documented environment variables and configuration fields

Validation

• make docs-lint
• make docs-typecheck
• cd apps/docs && bun run check:contracts
• docker compose config --quiet for both localized Compose examples
• make docs-build
• localized route smoke checks for six documentation routes