fix(pos): alert on waiter calls / guest orders on the POS & queue display

The call-waiter flow was fully wired (guest QR button → public endpoint →
NotifyCallWaiterAsync persists + broadcasts NotificationReceived), but the alert
hook (useOrderAlerts: sound + toast + desktop popup) and the bell live only in
the (dashboard) layout. During service staff are on the POS (fullscreen) layout,
which mounted neither — so a waiter call produced nothing where staff actually
stand. Mount useOrderAlerts in the (fullscreen) layout so POS / queue-display
get the chime + toast for waiter calls and new guest orders. (KDS is a dashboard
route, already covered.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/dashboard/src/app/[locale]/(fullscreen)/layout.tsx

@@ -6,6 +6,7 @@ import { Loader2 } from "lucide-react";
 import { useRouter } from "@/i18n/routing";
 import { useAuthStore } from "@/lib/stores/auth.store";
 import { RouteGuard } from "@/components/auth/route-guard";
+import { useOrderAlerts } from "@/lib/realtime/use-order-alerts";
 
 /** Full-viewport routes (POS, queue TV display) — auth only, no dashboard chrome. */
 export default function FullscreenLayout({ children }: { children: React.ReactNode }) {
@@ -15,6 +16,10 @@ export default function FullscreenLayout({ children }: { children: React.ReactNo
   const hasHydrated = useAuthStore((s) => s._hasHydrated);
   const dir = locale === "en" ? "ltr" : "rtl";
 
+  // Surface café notifications (waiter calls, new guest orders) on the POS /
+  // queue-display too — during service staff are here, not on the dashboard.
+  useOrderAlerts();
+
   useEffect(() => {
     // Only redirect AFTER the persisted auth has rehydrated from localStorage —
     // otherwise a page refresh sees the empty initial state and bounces an