Fix PWA installation support

app/globals.css

@@ -2,6 +2,8 @@
 @import "tw-animate-css";
 @import "../vendor/shadcn-tailwind-4.13.0.css";
 
+.pwa-install{position:fixed;z-index:60;right:1rem;bottom:1rem;display:flex;align-items:center;gap:.75rem;max-width:min(28rem,calc(100vw - 2rem));padding:.8rem .9rem;color:#eff6ff;background:rgba(15,23,42,.94);border:1px solid rgba(147,197,253,.45);border-radius:.85rem;box-shadow:0 12px 30px rgba(15,23,42,.28);font-size:.875rem}.pwa-install button{flex:none;padding:.45rem .7rem;border-radius:.55rem;border:0;background:#60a5fa;color:#0f172a;font-weight:700;cursor:pointer}.pwa-ios{color:#bfdbfe;white-space:nowrap}@media(max-width:520px){.pwa-install{left:.75rem;right:.75rem;bottom:.75rem;flex-wrap:wrap}.pwa-ios{white-space:normal}}
+
 @utility scrollbar-thin {
   scrollbar-width: thin;
 }

app/layout.tsx

@@ -8,6 +8,7 @@ export const metadata: Metadata = {
   icons: {
     icon: "/favicon.svg",
     shortcut: "/favicon.svg",
+    apple: "/icon-192.png",
   },
   manifest: "/manifest.webmanifest",
   applicationName: "大学英语六级 · 90天打卡",

app/pwa-register.tsx

@@ -1,3 +1,23 @@
 "use client";
-import { useEffect } from "react";
+import { useEffect, useState } from "react";
-export default function PwaRegister() { useEffect(() => { if ("serviceWorker" in navigator) navigator.serviceWorker.register("/sw.js").catch(() => undefined); }, []); return null; }
+
+type InstallPrompt = Event & { prompt: () => Promise<void>; userChoice: Promise<{ outcome: "accepted" | "dismissed" }> };
+
+export default function PwaRegister() {
+  const [prompt, setPrompt] = useState<InstallPrompt | null>(null);
+  const [isIos, setIsIos] = useState(false);
+
+  useEffect(() => {
+    if ("serviceWorker" in navigator) navigator.serviceWorker.register("/sw.js", { updateViaCache: "none" }).catch(() => undefined);
+    setIsIos(/iphone|ipad|ipod/i.test(navigator.userAgent));
+    const receivePrompt = (event: Event) => { event.preventDefault(); setPrompt(event as InstallPrompt); };
+    window.addEventListener("beforeinstallprompt", receivePrompt);
+    return () => window.removeEventListener("beforeinstallprompt", receivePrompt);
+  }, []);
+
+  if (!prompt && !isIos) return null;
+  return <div className="pwa-install" role="status">
+    <span>把打卡站点安装到桌面，打开更快捷。</span>
+    {prompt ? <button onClick={async () => { await prompt.prompt(); const result = await prompt.userChoice; if (result.outcome === "accepted") setPrompt(null); }}>安装应用</button> : <span className="pwa-ios">Safari 点“分享”→“添加到主屏幕”</span>}
+  </div>;
+}