feat: add Traditional Chinese (繁體中文) translation (#2770)

- Add res/values/strings_zh_TW.arb with Traditional Chinese translations
- Update lib/entities/language_service.dart to include zh_TW locale
- Update tool/utils/translation/translation_constants.dart to include zh-tw

This adds full Traditional Chinese (Taiwan) language support with proper
Taiwan-specific terminology (e.g., 啟用, 新增, 進階設定, 簽帳金融卡, etc.)

All simplified Chinese characters have been converted to traditional Chinese.

lib/entities/language_service.dart

@@ -17,7 +17,8 @@ class LanguageService {
     'pt': 'Português (Portuguese)',
     'ru': 'Русский (Russian)',
     'uk': 'Українська (Ukrainian)',
-    'zh': '中文 (Chinese)',
+    'zh': '简体中文 (Chinese Simplified)',
+    'zh_TW': '繁體中文 (Chinese Traditional)',
     'hr': 'Hrvatski (Croatian)',
     'it': 'Italiano (Italian)',
     'th': 'ภาษาไทย (Thai)',
@@ -50,6 +51,7 @@ class LanguageService {
     'ru': 'rus',
     'uk': 'ukr',
     'zh': 'chn',
+    'zh_TW': 'twn',
     'hr': 'hrv',
     'it': 'ita',
     'th': 'tha',
@@ -81,15 +83,15 @@ class LanguageService {
 
   static Future<String> localeDetection() async {
     try {
-        var locale = await Devicelocale.currentLocale ?? '';
-        locale = Intl.shortLocale(locale);
+      var locale = await Devicelocale.currentLocale ?? '';
+      locale = Intl.shortLocale(locale);
 
-        if (list.keys.contains(locale)) {
-            return locale;
-        }
-        return LanguageService.defaultLocale;
-    } catch(_) {
-        return LanguageService.defaultLocale;
+      if (list.keys.contains(locale)) {
+        return locale;
+      }
+      return LanguageService.defaultLocale;
+    } catch (_) {
+      return LanguageService.defaultLocale;
     }
   }
 }

tool/utils/translation/translation_constants.dart

@@ -2,5 +2,5 @@ const defaultLang = "en";
 const langs = [
   "ar", "bg", "cs", "de", "en", "es", "fr", "gn", "ha", "hi", "hr", "hy", "id", "it",
   "ja", "ko", "my", "nl", "pl", "pt", "ru", "th", "tl", "tr", "uk", "ur", "yo",
-  "vi", "zh-cn" // zh, but Google Translate uses zh-cn for Chinese (Simplified)
+  "vi", "zh-cn", "zh-tw" // zh-cn for Chinese (Simplified), zh-tw for Chinese (Traditional)
 ];