feat: add Traditional Chinese (zh-Hant) language option (#23322)

The zh-Hant translations are synced from Weblate (98% complete) but the
locale was never registered in the language selector, so users could not
select it. Register zh-Hant in supportedLanguageKeys, add its display
label, and map it to the zh-TW date-fns locale.

web/public/locales/en/common.json

@@ -177,6 +177,7 @@
       "en": "English (English)",
       "es": "Español (Spanish)",
       "zhCN": "简体中文 (Simplified Chinese)",
+      "zhHant": "繁體中文 (Traditional Chinese)",
       "hi": "हिन्दी (Hindi)",
       "fr": "Français (French)",
       "ar": "العربية (Arabic)",

web/src/components/menu/GeneralSettings.tsx

@@ -109,6 +109,7 @@ export default function GeneralSettings({ className }: GeneralSettingsProps) {
       "nb-NO": "nb",
       "yue-Hant": "yue",
       "zh-CN": "zhCN",
+      "zh-Hant": "zhHant",
       "pt-BR": "ptBR",
     };
 

web/src/hooks/use-date-locale.ts

@@ -34,6 +34,8 @@ const localeMap: Record<string, () => Promise<Locale>> = {
   sk: () => import("date-fns/locale/sk").then((module) => module.sk),
   "yue-Hant": () =>
     import("date-fns/locale/zh-HK").then((module) => module.zhHK),
+  "zh-Hant": () =>
+    import("date-fns/locale/zh-TW").then((module) => module.zhTW),
   lt: () => import("date-fns/locale/lt").then((module) => module.lt),
   th: () => import("date-fns/locale/th").then((module) => module.th),
   ca: () => import("date-fns/locale/ca").then((module) => module.ca),

web/src/lib/const.ts

@@ -29,6 +29,7 @@ export const supportedLanguageKeys = [
   "nb-NO",
   "sv",
   "zh-CN",
+  "zh-Hant",
   "yue-Hant",
   "ja",
   "vi",