feat: 添加加载保存语言的功能，优化语言管理逻辑

src/App.vue

@@ -1,6 +1,8 @@
 <script setup lang="ts">
 const { initializeWallet } = useWalletStore();
-const { locale } = useLanguage();
+const { locale, loadSavedLanguage } = useLanguage();
+
+loadSavedLanguage();
 
 onMounted(() => {
   initializeWallet();