fix(reminders): lifecycle-aware jobs and dispatch skip guard

The reminder pipeline fired regardless of what happened to the booking
after creation: cancelled customers got reminded about bookings that
weren't happening, reschedules kept the old reminder time, and
waitlisted bookings armed jobs too. Pending jobs are now cancelled on
both cancel paths, deleted and re-armed on reschedule, and dispatch
joins bookings.status to skip anything not confirmed. Reschedule also
gained the same availability-window and blocked-day validation as
booking creation, closing a 3am-reschedule hole via the manage URL.

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

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

apps/backend/internal/db/bookings.go

@@ -108,7 +108,7 @@ func (r *PGRepository) ListDueReminderJobs(ctx context.Context, dueBefore time.T
 	rows, err := r.pool.Query(ctx, `
 		SELECT rj.id, rj.tenant_id, t.name, t.locale, t.timezone,
 		       rj.booking_id, rj.channel, rj.scheduled_for,
-		       b.customer_name, b.customer_email, b.reference, b.starts_at, rj.status
+		       b.customer_name, b.customer_email, b.reference, b.starts_at, rj.status, b.status
 		FROM reminder_jobs rj
 		INNER JOIN bookings b ON b.id = rj.booking_id
 		INNER JOIN tenants t ON t.id = rj.tenant_id
@@ -138,6 +138,7 @@ func (r *PGRepository) ListDueReminderJobs(ctx context.Context, dueBefore time.T
 			&record.Reference,
 			&record.StartsAt,
 			&record.Status,
+			&record.BookingStatus,
 		); err != nil {
 			return nil, err
 		}
@@ -191,3 +192,20 @@ func (r *PGRepository) GetDashboardMetrics(ctx context.Context, tenantID string,
 	)
 	return metrics, err
 }
+
+func (r *PGRepository) CancelPendingReminderJobsForBooking(ctx context.Context, bookingID string) error {
+	_, err := r.pool.Exec(ctx, `
+		UPDATE reminder_jobs
+		SET status = 'cancelled'
+		WHERE booking_id = $1 AND status = 'pending'
+	`, bookingID)
+	return err
+}
+
+func (r *PGRepository) DeletePendingReminderJobsForBooking(ctx context.Context, bookingID string) error {
+	_, err := r.pool.Exec(ctx, `
+		DELETE FROM reminder_jobs
+		WHERE booking_id = $1 AND status = 'pending'
+	`, bookingID)
+	return err
+}