Fix stale social media preview: revalidate next-event fetch, reject past featured events

Made-with: Cursor

frontend/src/app/(public)/page.tsx

@@ -38,8 +38,10 @@ interface NextEvent {
 
 async function getNextUpcomingEvent(): Promise<NextEvent | null> {
   try {
+    const revalidateSeconds =
+      parseInt(process.env.NEXT_EVENT_REVALIDATE_SECONDS || '3600', 10) || 3600;
     const response = await fetch(`${apiUrl}/api/events/next/upcoming`, {
-      next: { tags: ['next-event'] },
+      next: { tags: ['next-event'], revalidate: revalidateSeconds },
     });
     if (!response.ok) return null;
     const data = await response.json();