feat: add cross-platform PWA install prompt

src/pages/LoginPage.tsx

@@ -4,6 +4,7 @@ import { Sparkles, ArrowRight, Mail, Lock, AlertCircle, Wand2 } from "lucide-rea
 import { useAuth } from "../lib/auth";
 import { api } from "../lib/api";
 import { Spinner } from "../components/ui";
+import { InstallAppPrompt } from "../components/InstallAppPrompt";
 
 const DEMO = import.meta.env.DEV || import.meta.env.VITE_DEMO_UI === "1";
 
@@ -156,6 +157,10 @@ export function LoginPage() {
               </button>
             </form>
 
+            <div className="mx-auto mt-4 max-w-sm">
+              <InstallAppPrompt />
+            </div>
+
             {DEMO && (
               <>
                 <div className="mt-5 flex items-center gap-2 text-xs font-medium text-slate-400">