feat: 添加 PWA 安装支持，包含安装提示和 iOS 指导页面

src/composables/usePWAInstall.ts

@@ -0,0 +1,101 @@
+interface BeforeInstallPromptEvent extends Event {
+  prompt: () => Promise<void>;
+  userChoice: Promise<{ outcome: "accepted" | "dismissed" }>;
+}
+
+export function usePWAInstall() {
+  const deferredPrompt = ref<BeforeInstallPromptEvent | null>(null);
+  const showInstallButton = ref(false);
+  const isInstalled = ref(false);
+
+  // 检查是否已安装
+  function checkIfInstalled() {
+    // 检查是否在独立模式下运行（已安装）
+    if (window.matchMedia("(display-mode: standalone)").matches) {
+      isInstalled.value = true;
+      console.log("[PWA] Already installed (standalone mode)");
+      return true;
+    }
+
+    // 检查 iOS Safari 独立模式
+    if ((window.navigator as any).standalone === true) {
+      isInstalled.value = true;
+      console.log("[PWA] Already installed (iOS standalone)");
+      return true;
+    }
+
+    return false;
+  }
+
+  // 检测是否是 iOS 设备
+  function isIOS() {
+    return /iPad|iPhone|iPod/.test(navigator.userAgent) && !(window as any).MSStream;
+  }
+
+  // 检测是否是 iOS Safari（未安装）
+  function isIOSSafari() {
+    return isIOS() && !(window.navigator as any).standalone;
+  }
+
+  // 在全局作用域设置监听器（不在 onMounted 中）
+  if (typeof window !== "undefined") {
+    // 检查是否已安装
+    if (!checkIfInstalled()) {
+      // 监听安装提示事件（仅 Android/Chrome）
+      window.addEventListener("beforeinstallprompt", (e: Event) => {
+        console.log("[PWA] beforeinstallprompt event fired");
+        e.preventDefault();
+        deferredPrompt.value = e as BeforeInstallPromptEvent;
+        showInstallButton.value = true;
+      });
+
+      // 监听安装成功事件
+      window.addEventListener("appinstalled", () => {
+        console.log("[PWA] App installed successfully");
+        deferredPrompt.value = null;
+        showInstallButton.value = false;
+        isInstalled.value = true;
+      });
+
+      // iOS 设备也显示安装按钮（iOS 不支持 beforeinstallprompt）
+      if (isIOSSafari()) {
+        console.log("[PWA] iOS Safari detected, showing install button");
+        showInstallButton.value = true;
+      }
+    }
+  }
+
+  async function promptInstall() {
+    // iOS 设备返回特殊标识，由组件处理
+    if (isIOSSafari()) {
+      console.log("[PWA] iOS: Showing manual install guide");
+      return { outcome: "ios-instruction" as const };
+    }
+
+    // Android/Chrome 设备
+    if (!deferredPrompt.value) {
+      console.log("[PWA] No deferred prompt available");
+      return { outcome: "not-available" as const };
+    }
+
+    console.log("[PWA] Showing install prompt");
+    await deferredPrompt.value.prompt();
+    const { outcome } = await deferredPrompt.value.userChoice;
+    console.log("[PWA] User choice:", outcome);
+
+    if (outcome === "accepted") {
+      showInstallButton.value = false;
+      deferredPrompt.value = null;
+    }
+
+    return { outcome };
+  }
+
+  return {
+    showInstallButton: computed(() => showInstallButton.value && !isInstalled.value),
+    isInstalled,
+    promptInstall,
+    isIOS: isIOS(),
+    isIOSSafari: isIOSSafari(),
+  };
+}