fix(admin): 登出按钮补 cursor-pointer

登出按钮缺少 cursor-pointer，鼠标悬停时仍显示文本光标而非手型，与
其他可点击元素不一致。

src/components/admin_layout.rs

@@ -84,7 +84,7 @@ pub fn AdminLayout() -> Element {
         div { class: "flex items-center gap-3",
             ThemeToggle {}
             button {
-                class: "text-sm text-paper-secondary hover:text-paper-primary transition-colors",
+                class: "text-sm text-paper-secondary hover:text-paper-primary transition-colors cursor-pointer",
                 onclick: move |_| {
                     spawn(async move {
                         let _ = logout().await;