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/db/schema.ts

@@ -75,7 +75,7 @@ export const sqliteEvents = sqliteTable('events', {
   price: real('price').notNull().default(0),
   currency: text('currency').notNull().default('PYG'),
   capacity: integer('capacity').notNull().default(50),
-  status: text('status', { enum: ['draft', 'published', 'cancelled', 'completed', 'archived'] }).notNull().default('draft'),
+  status: text('status', { enum: ['draft', 'published', 'unlisted', 'cancelled', 'completed', 'archived'] }).notNull().default('draft'),
   bannerUrl: text('banner_url'),
   externalBookingEnabled: integer('external_booking_enabled', { mode: 'boolean' }).notNull().default(false),
   externalBookingUrl: text('external_booking_url'),