Close pre-sale registration a configurable time before events start.

Events gain nullable presale_closure_enabled / presale_close_minutes_before
overrides; null inherits the new site_settings defaults (enabled, 120 min).
A shared resolver computes the effective cutoff, which the public event API
exposes as presaleClosesAt and the public booking endpoint enforces. Door and
admin ticket creation are not gated.

Admin: toggle + duration picker in the event modal (pre-filled from the site
default) and a matching default card on Settings › General. Public: the event
page shows "Registration Closed" after the cutoff and the checkout page
redirects back.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/src/app/(public)/events/[id]/EventDetailClient.tsx

@@ -5,7 +5,7 @@ import Link from 'next/link';
 import Image from 'next/image';
 import { useLanguage } from '@/context/LanguageContext';
 import { eventsApi, Event } from '@/lib/api';
-import { formatPrice, formatDateLong, formatTime, eventSpotsLeft, isEventSoldOut } from '@/lib/utils';
+import { formatPrice, formatDateLong, formatTime, eventSpotsLeft, isEventSoldOut, isPresaleClosed } from '@/lib/utils';
 import Card from '@/components/ui/Card';
 import Button from '@/components/ui/Button';
 import ShareButtons from '@/components/ShareButtons';
@@ -69,7 +69,9 @@ export default function EventDetailClient({ eventId, initialEvent }: EventDetail
   const isCancelled = event.status === 'cancelled';
   // Only calculate isPastEvent after mount to avoid hydration mismatch
   const isPastEvent = mounted ? new Date(event.startDatetime) < new Date() : false;
-  const canBook = !isSoldOut && !isCancelled && !isPastEvent && (event.status === 'published' || event.status === 'unlisted');
+  // Pre-sale closure (server-computed cutoff); same mount guard as isPastEvent
+  const presaleClosed = mounted ? isPresaleClosed(event) : false;
+  const canBook = !isSoldOut && !isCancelled && !isPastEvent && !presaleClosed && (event.status === 'published' || event.status === 'unlisted');
 
   // Booking card content - reused for mobile and desktop positions
   const BookingCardContent = () => (
@@ -143,11 +145,21 @@ export default function EventDetailClient({ eventId, initialEvent }: EventDetail
         <Button className="w-full" size="lg" disabled>
           {isPastEvent 
             ? t('events.details.eventEnded')
+            : presaleClosed
+              ? t('events.details.registrationClosed')
             : isSoldOut 
               ? t('events.details.soldOut') 
               : t('events.details.cancelled')}
         </Button>
       )}
+
+      {canBook && !event.externalBookingEnabled && event.presaleClosesAt && (
+        <p className="mt-3 text-center text-xs text-gray-500">
+          {t('events.details.registrationClosesAt', {
+            date: `${formatDate(event.presaleClosesAt)} ${fmtTime(event.presaleClosesAt)}`,
+          })}
+        </p>
+      )}
       
       {!event.externalBookingEnabled && (
         <p className="mt-4 text-center text-sm text-gray-500">

frontend/src/app/(public)/events/[id]/page.tsx

@@ -25,6 +25,7 @@ interface Event {
   bannerUrl?: string;
   availableSeats?: number;
   bookedCount?: number;
+  presaleClosesAt?: string | null;
   createdAt: string;
   updatedAt: string;
 }
@@ -125,6 +126,7 @@ function generateEventJsonLd(event: Event) {
         : 'https://schema.org/SoldOut',
       url: `${siteUrl}/events/${event.slug}`,
       validFrom: new Date().toISOString(),
+      ...(event.presaleClosesAt ? { validThrough: event.presaleClosesAt } : {}),
     },
     image: event.bannerUrl
       ? (event.bannerUrl.startsWith('http') ? event.bannerUrl : `${siteUrl}${event.bannerUrl}`)