fix(认证): 订阅兑换失效认证缓存

订阅兑换后同步失效认证缓存避免授权快照滞后
补充单测覆盖订阅兑换的失效场景

测试: go test ./... -tags=unit

backend/internal/service/auth_cache_invalidation_test.go

@@ -26,6 +26,8 @@ func TestRedeemService_InvalidateRedeemCaches_AuthCache(t *testing.T) {
 
 	svc.invalidateRedeemCaches(context.Background(), 11, &RedeemCode{Type: RedeemTypeBalance})
 	svc.invalidateRedeemCaches(context.Background(), 11, &RedeemCode{Type: RedeemTypeConcurrency})
+	groupID := int64(3)
+	svc.invalidateRedeemCaches(context.Background(), 11, &RedeemCode{Type: RedeemTypeSubscription, GroupID: &groupID})
 
-	require.Equal(t, []int64{11, 11}, invalidator.userIDs)
+	require.Equal(t, []int64{11, 11, 11}, invalidator.userIDs)
 }

backend/internal/service/redeem_service.go

@@ -348,6 +348,9 @@ func (s *RedeemService) invalidateRedeemCaches(ctx context.Context, userID int64
 			return
 		}
 	case RedeemTypeSubscription:
+		if s.authCacheInvalidator != nil {
+			s.authCacheInvalidator.InvalidateAuthCacheByUserID(ctx, userID)
+		}
 		if s.billingCacheService == nil {
 			return
 		}