feat(pwa): mount PWAInstallPrompt in admin layout

src/app/admin/layout.tsx

@@ -11,6 +11,7 @@ import { ToastContainer } from "@/components/admin/ToastContainer";
 import { SmoothViewTransition } from "@/components/transitions/SmoothViewTransition";
 import { RouteAnnouncer } from "@/components/transitions/RouteAnnouncer";
 import CommandPalette from "@/components/admin/CommandPalette";
+import PWAInstallPrompt from "@/components/pwa/InstallPrompt";
 import { getEnabledAddons } from "@/actions/billing/stripe-portal";
 
 // Admin layout calls getAdminUser() which reads cookies(). Without this,
@@ -135,6 +136,7 @@ export default async function AdminLayout({ children }: { children: React.ReactN
         <SmoothViewTransition>{children}</SmoothViewTransition>
         <RouteAnnouncer />
       </div>
+      <PWAInstallPrompt />
     </ToastProviderWrapper>
   );
 }