fix: P1 activation path hardening - Bug 4-9

Bug 4: resolveRenewalActivationSubscription - add fallback by user_id+subscribe_id
  with SELECT FOR UPDATE when token lookup fails

Bug 5: appleIAPNotifyLogic - return error on product ID mapping failure instead of
  silently dropping the notification

Bug 6: NewPurchase fallback query - wrap in transaction with SELECT FOR UPDATE to
  prevent concurrent duplicate subscription creation

Bug 7: appleIAPNotifyLogic - fix UserId=0 by reverse-lookup from original purchase
  order; create renewal audit order record for DID_RENEW/SUBSCRIBED notifications

Bug 8: UpdateOrderStatus - pre-delete cache before DB write (double-delete) to
  close TOCTOU window between DB update and cache invalidation

Bug 9: validateNewUserOnlyEligibilityAtActivation - add Redis distributed lock on
  user_id to serialise concurrent new-user-only order activations

Co-authored-by: multica-agent <github@multica.ai>

internal/model/order/model.go

@@ -110,6 +110,10 @@ func (m *customOrderModel) UpdateOrderStatus(ctx context.Context, orderNo string
 	if err != nil {
 		return err
 	}
+	keys := m.getCacheKeys(orderInfo)
+	// Pre-delete: evict cache before the DB write so concurrent reads during the update
+	// window go to DB instead of getting a stale cached status (double-delete pattern).
+	_ = m.DelCacheCtx(ctx, keys...)
 	return m.ExecCtx(ctx, func(conn *gorm.DB) error {
 		if len(tx) > 0 {
 			conn = tx[0]
@@ -123,7 +127,7 @@ func (m *customOrderModel) UpdateOrderStatus(ctx context.Context, orderNo string
 			return nil
 		}
 		return nil
-	}, m.getCacheKeys(orderInfo)...)
+	}, keys...)
 }
 
 // FindOneDetailsByOrderNo Find order details by order number