fix(lint): 修复 CI 中的 ineffassign 和 unused 代码告警，修正 group 排序集成测试兼容性

backend/internal/handler/admin/usage_handler_request_type_test.go

@@ -17,7 +17,6 @@ type adminUsageRepoCapture struct {
 	service.UsageLogRepository
 	listParams   pagination.PaginationParams
 	listFilters  usagestats.UsageLogFilters
-	statsParams  pagination.PaginationParams
 	statsFilters usagestats.UsageLogFilters
 }