[DOCS] zh translation

[bnbong]

Requesting Merging

Description

Closes #61
Refs #59
Refs #60

Add complete Chinese (zh) documentation localization across the FastAPI-fastkit docs site.

This PR completes the Chinese locale rollout by landing the translated pages under docs/zh/ across user-guide, tutorial, contributing, and reference sections. It also updates the translation status pages to reflect that Chinese is now fully covered (26 / 26) and keeps the localized changelog page as a wrapper around the canonical root CHANGELOG.md.

Type of Change

• BUG FIX
• ADDING NEW TEMPLATE
• FEATURE ADDED/UPDATED
• HOTFIX
• DELETING UNNECESSARY FEATURES
• DOCUMENTATION & DEVOPS
• Etc..

Test Environment

• OS: macOS
• Python: 3.12
• Validation command:
  • uv run mkdocs build

Major Changes

• Added the complete Chinese locale documentation under docs/zh/
• Completed the Chinese translation rollout across all planned phases
• Updated docs/en/reference/translation-status.md and docs/zh/reference/translation-status.md to mark Chinese as 26 / 26 complete
• Added docs/zh/changelog.md as a wrapper entry that reuses the canonical English CHANGELOG.md
• Polished translated wording so the Chinese docs read naturally while preserving commands, file paths, env vars, template IDs, and product names in English per the translation workflow

Screenshots (optional)

• N/A

Etc

N/A

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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