Add unlisted event status: hidden from listings but accessible by URL

- Backend: add 'unlisted' to schema enum and Zod validation; allow booking for unlisted events
- Frontend: Event type and guards updated; unlisted events bookable, excluded from public listing/sitemap
- Admin: badge, status dropdown, Make Unlisted / Make Public / Unpublish actions; scanner/emails/tickets include unlisted

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/routes/tickets.ts

@@ -69,7 +69,7 @@ ticketsRouter.post('/', zValidator('json', createTicketSchema), async (c) => {
     return c.json({ error: 'Event not found' }, 404);
   }
   
-  if (event.status !== 'published') {
+  if (!['published', 'unlisted'].includes(event.status)) {
     return c.json({ error: 'Event is not available for booking' }, 400);
   }