feat(waitlist): queue position on the customer manage page

A waitlisted customer saw only a bare status — worse, the badge fell
back to "Pending" for both waitlisted and cancelled states. The view
now carries a 1-based waitlistPosition (earlier-created waitlisted
bookings on the session + 1) and the page renders a warning-tone
notice with the queue spot and auto-promotion explanation, in CS/EN.
Also fixed the badge's nonexistent --danger-soft/--warning-soft tokens.

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

@@ -204,6 +204,18 @@ func (r *PGRepository) GetDashboardMetrics(ctx context.Context, tenantID string,
 	return metrics, err
 }
 
+func (r *PGRepository) GetWaitlistPosition(ctx context.Context, sessionID, bookingID string) (int, error) {
+	var position int
+	err := r.pool.QueryRow(ctx, `
+		SELECT COUNT(*) + 1
+		FROM bookings
+		WHERE class_session_id = $1
+			AND status = 'waitlisted'
+			AND created_at < (SELECT created_at FROM bookings WHERE id = $2)
+	`, sessionID, bookingID).Scan(&position)
+	return position, err
+}
+
 func (r *PGRepository) CancelPendingReminderJobsForBooking(ctx context.Context, bookingID string) error {
 	_, err := r.pool.Exec(ctx, `
 		UPDATE reminder_jobs