fix(reminders): re-arm reminder jobs on waitlist promotion

A booking promoted off the waitlist after its reminder had already
dispatched-as-skipped went unreminded. Promotion now clears pending
jobs and re-arms via the shared armReminderJobs helper — extracted
from booking creation so both paths arm email plus opt-in SMS.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/bookings/service.go

@@ -357,26 +357,8 @@ func (s *Service) Create(ctx context.Context, request domain.CreateBookingReques
 		}
 	}
 
-	if scheduledFor, ok := reminderSchedule(startsAt); ok {
-		if err := s.repo.CreateReminderJob(ctx, db.ReminderJobParams{
-			TenantID:     tenant.ID,
-			BookingID:    created.ID,
-			Channel:      "email",
-			ScheduledFor: scheduledFor,
-		}); err != nil {
-			return domain.CreateBookingResponse{}, err
-		}
-		// SMS reminders are a per-tenant opt-in and need a customer phone.
-		if request.CustomerPhone != "" {
-			if smsSettings, err := s.repo.GetTenantSMSSettings(ctx, tenant.ID); err == nil && smsSettings.Enabled {
-				_ = s.repo.CreateReminderJob(ctx, db.ReminderJobParams{
-					TenantID:     tenant.ID,
-					BookingID:    created.ID,
-					Channel:      "sms",
-					ScheduledFor: scheduledFor,
-				})
-			}
-		}
+	if err := armReminderJobs(ctx, s.repo, tenant.ID, created.ID, startsAt, request.CustomerPhone); err != nil {
+		return domain.CreateBookingResponse{}, err
 	}
 
 	// Send confirmation emails (async - don't fail booking if email fails)