fix(admin): resolve CI lint and user subscriptions regression

backend/internal/handler/admin/account_today_stats_cache.go

@@ -35,12 +35,12 @@ func buildAccountTodayStatsBatchCacheKey(accountIDs []int64) string {
 	}
 	var b strings.Builder
 	b.Grow(len(accountIDs) * 6)
-	b.WriteString("accounts_today_stats:")
+	_, _ = b.WriteString("accounts_today_stats:")
 	for i, id := range accountIDs {
 		if i > 0 {
-			b.WriteByte(',')
+			_ = b.WriteByte(',')
 		}
-		b.WriteString(strconv.FormatInt(id, 10))
+		_, _ = b.WriteString(strconv.FormatInt(id, 10))
 	}
 	return b.String()
 }

backend/internal/handler/admin/user_handler.go

@@ -90,7 +90,10 @@ func (h *UserHandler) List(c *gin.Context) {
 		Role:       c.Query("role"),
 		Search:     search,
 		Attributes: parseAttributeFilters(c),
-		IncludeSubscriptions: parseBoolQueryWithDefault(c.Query("include_subscriptions"), true),
+	}
+	if raw, ok := c.GetQuery("include_subscriptions"); ok {
+		includeSubscriptions := parseBoolQueryWithDefault(raw, true)
+		filters.IncludeSubscriptions = &includeSubscriptions
 	}
 
 	users, total, err := h.adminService.ListUsers(c.Request.Context(), page, pageSize, filters)

backend/internal/repository/user_repo.go

@@ -243,7 +243,8 @@ func (r *userRepository) ListWithFilters(ctx context.Context, params pagination.
 		userMap[u.ID] = &outUsers[len(outUsers)-1]
 	}
 
-	if filters.IncludeSubscriptions {
+	shouldLoadSubscriptions := filters.IncludeSubscriptions == nil || *filters.IncludeSubscriptions
+	if shouldLoadSubscriptions {
 		// Batch load active subscriptions with groups to avoid N+1.
 		subs, err := r.client.UserSubscription.Query().
 			Where(

backend/internal/service/user_service.go

@@ -24,7 +24,8 @@ type UserListFilters struct {
 	Attributes map[int64]string // Custom attribute filters: attributeID -> value
 	// IncludeSubscriptions controls whether ListWithFilters should load active subscriptions.
 	// For large datasets this can be expensive; admin list pages should enable it on demand.
-	IncludeSubscriptions bool
+	// nil means not specified (default: load subscriptions for backward compatibility).
+	IncludeSubscriptions *bool
 }
 
 type UserRepository interface {