feat: 添加加载中提示，更新下载页面的显示逻辑

src/locales/ar.json

@@ -1015,6 +1015,7 @@
       "nativeAppDesc": "بالفعل أحدث إصدار",
       "notSupportedTitle": "المتصفح غير مدعوم",
       "notSupportedDesc": "يرجى استخدام Chrome أو Safari أو Edge",
+      "loading": "جاري التحميل...",
       "iosInstallHeader": "دليل التثبيت على iOS",
       "iosInstallMessage": "اضغط على زر المشاركة في الأسفل واختر 'إضافة إلى الشاشة الرئيسية'",
       "iosInstallButton": "حسناً",

src/locales/en-US.json

@@ -1015,6 +1015,7 @@
       "nativeAppDesc": "Already latest version",
       "notSupportedTitle": "Browser not supported",
       "notSupportedDesc": "Please use Chrome, Safari, or Edge",
+      "loading": "Loading...",
       "iosInstallHeader": "iOS Installation Guide",
       "iosInstallMessage": "Tap the share button at the bottom and select 'Add to Home Screen'",
       "iosInstallButton": "Got it",

src/locales/zh-CN.json

@@ -1015,6 +1015,7 @@
       "nativeAppDesc": "已经是最新版本，无需下载",
       "notSupportedTitle": "当前浏览器暂不支持应用安装",
       "notSupportedDesc": "建议使用 Chrome、Safari 或 Edge 浏览器",
+      "loading": "加载中...",
       "iosInstallHeader": "iOS 安装指引",
       "iosInstallMessage": "请点击浏览器底部的分享按钮，然后选择\"添加到主屏幕\"",
       "iosInstallButton": "知道了",

src/locales/zh-HK.json

@@ -1015,6 +1015,7 @@
       "nativeAppDesc": "已經是最新版本，無需下載",
       "notSupportedTitle": "當前瀏覽器暫不支持應用安裝",
       "notSupportedDesc": "建議使用 Chrome、Safari 或 Edge 瀏覽器",
+      "loading": "加載中...",
       "iosInstallHeader": "iOS 安裝指引",
       "iosInstallMessage": "請點擊瀏覽器底部的分享按鈕，然後選擇\"添加到主屏幕\"",
       "iosInstallButton": "知道了",

src/views/pwa/download.vue

@@ -29,13 +29,20 @@ const wasUninstalled = computed(() => {
   return wasInstalled === "true" && !isInstalled.value;
 });
 
-// 显示下载按钮的条件
+// 显示下载按钮的条件：浏览器环境 + 未安装 + (能安装 或 非iOS)
 const shouldShowDownloadButton = computed(() => {
-  const result = platform === "browser" && !isInstalled.value;
+  const result = platform === "browser" && !isInstalled.value && (canInstall.value || !isIOS);
   console.log("[Download Page] shouldShowDownloadButton:", result);
   return result;
 });
 
+// 是否显示不支持提示：浏览器环境 + 不能安装 + 非iOS
+const shouldShowNotSupported = computed(() => {
+  const result = platform === "browser" && !canInstall.value && !isIOS && !isInstalled.value;
+  console.log("[Download Page] shouldShowNotSupported:", result);
+  return result;
+});
+
 // 处理安装
 async function handleInstall() {
   if (isIOSSafari) {
@@ -243,7 +250,7 @@ watch(isInstalled, (installed) => {
         </div>
 
         <!-- 浏览器不支持提示 -->
-        <div v-else class="w-full max-w-md">
+        <div v-else-if="shouldShowNotSupported" class="w-full max-w-md">
           <div class="bg-warning/10 border border-warning/20 rounded-2xl p-6 text-center">
             <p class="text-sm text-text-600">
               {{ t("pwa.download.notSupportedTitle") }}
@@ -253,6 +260,16 @@ watch(isInstalled, (installed) => {
             </p>
           </div>
         </div>
+
+        <!-- 其他情况：加载中或未知状态 -->
+        <div v-else class="w-full max-w-md">
+          <div class="bg-background-secondary rounded-2xl p-6 text-center">
+            <ion-spinner name="crescent" class="mx-auto mb-4" />
+            <p class="text-sm text-text-500">
+              {{ t("pwa.download.loading") }}
+            </p>
+          </div>
+        </div>
       </div>
     </ion-content>
   </ion-page>