修复iOS下载链接的条件渲染，确保仅在存在时显示下载按钮

src/views/AppDetail.vue

@@ -29,9 +29,13 @@ const app = computed(() => apps.find((item) => item.id === route.params.id));
         <p class="description">{{ app.description[locale] }}</p>
 
         <div class="actions">
-          <a :href="app.downloads.ios" target="_blank" rel="noreferrer">{{
-            t("iOS 下载", "Download for iOS")
-          }}</a>
+          <a
+            v-if="app.downloads.ios"
+            :href="app.downloads.ios"
+            target="_blank"
+            rel="noreferrer"
+            >{{ t("iOS 下载", "Download for iOS") }}</a
+          >
           <a :href="app.downloads.android" target="_blank" rel="noreferrer">{{
             t("Android 下载", "Download for Android")
           }}</a>