feat(i18n): add complete German (de) frontend locale support

web/src/components/layout/headerbar/LanguageSelector.jsx

@@ -45,6 +45,12 @@ const LanguageSelector = ({ currentLang, onLanguageChange, t }) => {
           >
             English
           </Dropdown.Item>
+          <Dropdown.Item
+            onClick={() => onLanguageChange('de')}
+            className={`!px-3 !py-1.5 !text-sm !text-semi-color-text-0 dark:!text-gray-200 ${currentLang === 'de' ? '!bg-semi-color-primary-light-default dark:!bg-blue-600 !font-semibold' : 'hover:!bg-semi-color-fill-1 dark:hover:!bg-gray-600'}`}
+          >
+            Deutsch
+          </Dropdown.Item>
           <Dropdown.Item
             onClick={() => onLanguageChange('fr')}
             className={`!px-3 !py-1.5 !text-sm !text-semi-color-text-0 dark:!text-gray-200 ${currentLang === 'fr' ? '!bg-semi-color-primary-light-default dark:!bg-blue-600 !font-semibold' : 'hover:!bg-semi-color-fill-1 dark:hover:!bg-gray-600'}`}

web/src/components/settings/personal/cards/PreferencesSettings.jsx

@@ -30,6 +30,7 @@ const languageOptions = [
 	{ value: "zh-CN", label: "简体中文" },
 	{ value: "zh-TW", label: "繁體中文" },
 	{ value: "en", label: "English" },
+	{ value: "de", label: "Deutsch" },
 	{ value: 'fr', label: 'Français'},
 	{ value: 'ru', label: 'Русский'},
 	{ value: 'ja', label: '日本語'},

web/src/i18n/i18n.js

@@ -28,6 +28,7 @@ import zhTWTranslation from './locales/zh-TW.json';
 import ruTranslation from './locales/ru.json';
 import jaTranslation from './locales/ja.json';
 import viTranslation from './locales/vi.json';
+import deTranslation from './locales/de.json';
 import { supportedLanguages } from './language';
 
 i18n
@@ -44,6 +45,7 @@ i18n
       ru: ruTranslation,
       ja: jaTranslation,
       vi: viTranslation,
+      de: deTranslation,
     },
     fallbackLng: 'zh-CN',
     nsSeparator: false,

web/src/i18n/language.js

@@ -25,6 +25,7 @@ export const supportedLanguages = [
   'ru',
   'ja',
   'vi',
+  'de',
 ];
 
 export const normalizeLanguage = (language) => {
@@ -53,6 +54,10 @@ export const normalizeLanguage = (language) => {
     return 'zh-TW';
   }
 
+  if (lower === 'de' || lower.startsWith('de-')) {
+    return 'de';
+  }
+
   const matchedLanguage = supportedLanguages.find(
     (supportedLanguage) => supportedLanguage.toLowerCase() === lower,
   );