feat(i18n): add Traditional Chinese Taiwan and Hong Kong locales (#2558)

Co-authored-by: Carlos Florencio <carlosmflorencio@gmail.com>

docs/i18n.md

@@ -2,9 +2,13 @@
 
 Kandev's web UI is internationalized with [i18next](https://www.i18next.com) +
 [react-i18next](https://react.i18next.com). English is the source locale,
-European Portuguese (`pt-pt`) and Simplified Chinese (`zh-cn`) are the shipped
+European Portuguese (`pt-pt`), Simplified Chinese (`zh-cn`), Traditional Chinese
+Taiwan (`zh-tw`), and Traditional Chinese Hong Kong (`zh-hk`) are the shipped
 human locales, and a generated **pseudo-locale** is used for QA. Requirements live in
-[`docs/specs/platform/i18n.md`](specs/platform/i18n.md).
+[`docs/specs/platform/i18n.md`](specs/platform/i18n.md). Traditional Chinese
+catalogs are derived from `zh-cn` via OpenCC plus a product glossary; see
+[`docs/specs/platform/traditional-chinese-locales.md`](specs/platform/traditional-chinese-locales.md)
+and [`docs/plans/traditional-chinese-locales/`](plans/traditional-chinese-locales/).
 
 The migration is **complete**. Every routed web UI surface renders through `t()`
 / `<Trans>`, and `i18nGuardFiles` now enumerates the directories that hold them.
@@ -1073,14 +1077,21 @@ Do it in its own PR, not inside a copy-only migration.
 Use a canonical lowercase locale id such as `zh-cn`. Locale negotiation accepts
 case variants such as `zh-CN`, but cookies and `<html lang>` use the canonical id.
 
+For Traditional Chinese Taiwan / Hong Kong specifically, prefer converting from
+`zh-cn` with `node scripts/convert-zh-cn-to-zh-hant.mjs --write` (OpenCC +
+`scripts/lib/zh-hant-glossary.json`) rather than re-translating from English.
+See `docs/plans/traditional-chinese-locales/glossary.md`.
+
 1. Add the locale to `SUPPORTED_LOCALES` and give it a fixed endonym in
    `LOCALE_LABELS` in `apps/web/lib/i18n/index.ts`. Add the same id to
    `supportedLocales` in `apps/backend/internal/i18n/i18n.go`. Keep the frontend
-   and backend lists synchronized.
+   and backend lists synchronized. Also wire `date-locale.ts` when the locale
+   needs a non-English date-fns pack.
 2. Copy every `apps/web/src/locales/en/*.json` namespace into
-   `apps/web/src/locales/<locale>/`. Translate values only: never rename keys,
-   plural suffixes, interpolation placeholders, `<Trans>` tags, command tokens,
-   shortcuts, filenames, URLs, or brand names.
+   `apps/web/src/locales/<locale>/` (or generate from `zh-cn` for Traditional
+   Chinese). Translate values only: never rename keys, plural suffixes,
+   interpolation placeholders, `<Trans>` tags, command tokens, shortcuts,
+   filenames, URLs, or brand names.
 3. Add `apps/backend/internal/i18n/locales/<locale>.json` with exactly the same
    keys as the backend `en.json` and translate its values.
 4. Add focused frontend tests for registration, selection, activation, cookie