Trigger Booking Sync Endpoint

Queue a reservation import for this tenant.

MANAGE_SETTINGS, not the page's VIEW_REPORTS: this reaches out to the customer's provider account, so it is an admin action rather than something every viewer of /bookings can fire.

Returns immediately — progress is read from /bookings/sync-state, whose backfill_started_at/backfill_completed_at/last_error the job stamps per property.