feat: 添加加载保存语言的功能，优化语言管理逻辑

src/composables/useLanguage.ts

@@ -11,6 +11,7 @@ export interface Language {
  */
 export function useLanguage() {
   const { locale, availableLocales } = useI18n();
+  const language = useStorage<Locale>("app-language", locale.value);
 
   // 可用的语言列表
   const languages: Language[] = [
@@ -36,17 +37,15 @@ export function useLanguage() {
    */
   function setLanguage(langCode: Locale) {
     locale.value = langCode;
-    // 持久化到 localStorage
-    localStorage.setItem("app-language", langCode);
+    language.value = langCode;
   }
 
   /**
    * 从 localStorage 加载保存的语言
    */
   function loadSavedLanguage() {
-    const saved = localStorage.getItem("app-language") as Locale;
-    if (saved && availableLocales.includes(saved)) {
-      locale.value = saved;
+    if (language.value && availableLocales.includes(language.value)) {
+      locale.value = language.value;
     }
   }