增加侧边栏持久化记忆

src/layouts/MainLayout.vue

@@ -82,10 +82,12 @@ const router = useRouter();
 const route = useRoute();
 const user = reactive({ name: "..." });
 
-// 侧边栏折叠状态
-const sidebarCollapsed = ref(false);
+// 侧边栏折叠状态（持久化到 localStorage，刷新后保持）
+const SIDEBAR_STORAGE_KEY = "sidebar_collapsed";
+const sidebarCollapsed = ref(localStorage.getItem(SIDEBAR_STORAGE_KEY) === "1");
 const toggleSidebar = () => {
   sidebarCollapsed.value = !sidebarCollapsed.value;
+  localStorage.setItem(SIDEBAR_STORAGE_KEY, sidebarCollapsed.value ? "1" : "0");
 };
 
 onMounted(() => {