fix(i18n): harden language switching and enforce language list consistency

src/utils/constants.ts

@@ -5,6 +5,10 @@
 
 import type { Language } from '@/types';
 
+const defineLanguageOrder = <T extends readonly Language[]>(
+  languages: T & ([Language] extends [T[number]] ? unknown : never)
+) => languages;
+
 // 缓存过期时间（毫秒）
 export const CACHE_EXPIRY_MS = 30 * 1000; // 与基线保持一致，减少管理端压力
 
@@ -36,13 +40,13 @@ export const STORAGE_KEY_SIDEBAR = 'cli-proxy-sidebar-collapsed';
 export const STORAGE_KEY_AUTH_FILES_PAGE_SIZE = 'cli-proxy-auth-files-page-size';
 
 // 语言配置
-export const LANGUAGE_ORDER: Language[] = ['zh-CN', 'en', 'ru'];
+export const LANGUAGE_ORDER = defineLanguageOrder(['zh-CN', 'en', 'ru'] as const);
 export const LANGUAGE_LABEL_KEYS: Record<Language, string> = {
   'zh-CN': 'language.chinese',
   en: 'language.english',
   ru: 'language.russian'
 };
-export const SUPPORTED_LANGUAGES: Language[] = LANGUAGE_ORDER;
+export const SUPPORTED_LANGUAGES = LANGUAGE_ORDER;
 
 // 通知持续时间
 export const NOTIFICATION_DURATION_MS = 3000;

src/utils/language.ts

@@ -1,16 +1,19 @@
 import type { Language } from '@/types';
 import { STORAGE_KEY_LANGUAGE, SUPPORTED_LANGUAGES } from '@/utils/constants';
 
+export const isSupportedLanguage = (value: string): value is Language =>
+  SUPPORTED_LANGUAGES.includes(value as Language);
+
 const parseStoredLanguage = (value: string): Language | null => {
   try {
     const parsed = JSON.parse(value);
     const candidate = parsed?.state?.language ?? parsed?.language ?? parsed;
-    if (SUPPORTED_LANGUAGES.includes(candidate as Language)) {
-      return candidate as Language;
+    if (typeof candidate === 'string' && isSupportedLanguage(candidate)) {
+      return candidate;
     }
   } catch {
-    if (SUPPORTED_LANGUAGES.includes(value as Language)) {
-      return value as Language;
+    if (isSupportedLanguage(value)) {
+      return value;
     }
   }
   return null;