feat(i18n): add Traditional Chinese localization (#3093)

* Add Traditional Chinese localization

* fix: address zh-TW formatting and token units

- Format `zh-TW.json` with Prettier.
- Use Traditional Chinese `萬` and `億` units for zh-TW token summaries.
- Add usage formatting coverage for Traditional Chinese locale aliases.

---------

Co-authored-by: Jason <farion1231@gmail.com>

src/components/settings/LanguageSettings.tsx

@@ -2,7 +2,7 @@ import { Button } from "@/components/ui/button";
 import { cn } from "@/lib/utils";
 import { useTranslation } from "react-i18next";
 
-type LanguageOption = "zh" | "en" | "ja";
+type LanguageOption = "zh" | "zh-TW" | "en" | "ja";
 
 interface LanguageSettingsProps {
   value: LanguageOption;
@@ -24,6 +24,12 @@ export function LanguageSettings({ value, onChange }: LanguageSettingsProps) {
         <LanguageButton active={value === "zh"} onClick={() => onChange("zh")}>
           {t("settings.languageOptionChinese")}
         </LanguageButton>
+        <LanguageButton
+          active={value === "zh-TW"}
+          onClick={() => onChange("zh-TW")}
+        >
+          {t("settings.languageOptionTraditionalChinese")}
+        </LanguageButton>
         <LanguageButton active={value === "en"} onClick={() => onChange("en")}>
           {t("settings.languageOptionEnglish")}
         </LanguageButton>