Traditional Chinese (zh-TW) translation of the documentation site

[allen0099]

Summary

The documentation site (https://fastapi-cachex.readthedocs.io/en/latest/) has been English-only since #85. docs/README.zh-TW.md still exists for GitHub readers, but it is not in the site navigation, and it predates the #85 corrections.

Read the Docs serves translations as separate projects linked to the main one. The result is /zh-tw/latest/ with a language switcher on the site.

Decisions

See the decision comment below for details.

• English is the source of truth; the translation may lag. Doc PRs do not need to update both languages. Each Chinese page shows a "may be outdated" notice that links to the English original.
• Scope: the landing page and the user guides. DEVELOPMENT.md, CONTRIBUTING.md, the CHANGELOG and the API reference stay English-only, and the Chinese nav links to the English pages for them.
• Terminology: Taiwan usage. Code, parameter and header names stay untranslated. A glossary lives at i18n/zh-TW/GLOSSARY.md.

Tracking

This issue spans several PRs. Each PR references it with Part of #89; only the last one closes it.

PR 1: infrastructure (#146)

• Second Zensical config (zensical.zh-TW.toml, docs_dir = "i18n/zh-TW/docs", language = "zh-Hant", own site_url)
• Chinese pages live outside docs/, so the English build does not pick them up (Zensical ignores exclude_docs)
• Language switcher on both sites
• "May be outdated" notice on every Chinese page
• Second .readthedocs.yaml for the Chinese project (i18n/zh-TW/.readthedocs.yaml)
• Docs CI builds both configs in strict mode
• Chinese landing page, replacing docs/README.zh-TW.md; untranslated guides link to the English site
• Glossary
• CONTRIBUTING and DEVELOPMENT state the sync policy

Read the Docs setup (maintainer, after PR 1)

• Create the fastapi-cachex-zh-tw project, set its language to Traditional Chinese, and point its build configuration file at i18n/zh-TW/.readthedocs.yaml
• Add it under the main project's Translations
• Check that /zh-tw/latest/ builds and that the language switcher works

PR 2: guides (#147)

• HTTP caching
• Cache flow
• Application cache
• Backends
• State

PR 3: session guides (closes this issue) (#148)

• Session
• JWT claims

[allen0099]

Decisions

1. Sync policy: English is the source of truth; the translation may lag. Doc changes do not have to update both languages in the same PR. Every Chinese page shows a notice that it may be outdated and links to the English original. CONTRIBUTING will say so.
2. Scope: the landing page and all user guides (HTTP caching, Cache flow, Application cache, Backends, Session, JWT claims, State). DEVELOPMENT.md, CONTRIBUTING.md, the CHANGELOG and the API reference stay English-only. The Chinese navigation links to the English pages for these.
3. Three PRs:
   1. Infrastructure: second Zensical config, Read the Docs config, CI, the Chinese landing page, and docs/README.zh-TW.md slimmed to match the English README. Guides that are not translated yet link to the English site. After this merges, the Read the Docs translation project can be created and the pipeline checked end to end.
   2. HTTP caching, Cache flow, Application cache, Backends, State.
   3. Session and JWT claims.
4. Terminology: Taiwan usage (快取, 後端, 標頭, 中介軟體, 權杖, ...). Code, parameter names and HTTP header names stay untranslated. A glossary under docs/zh-TW/ keeps later PRs consistent.