fix(lint): 修复所有golangci-lint错误

- 修复depguard错误：为ops service文件添加redis导入例外
- 修复errcheck错误：添加错误检查和类型断言检查
- 修复gofmt错误：格式化代码
- 修复ineffassign错误：移除无效的idx++赋值
- 修复staticcheck错误：合并条件赋值
- 修复unused错误：移除未使用的字段和函数
  - ops_cleanup_service.go: entryID字段
  - ops_retry.go: status字段
  - ops_upstream_context.go: getOpsUpstreamErrors函数

backend/internal/repository/ops_repo_dashboard.go

@@ -344,12 +344,12 @@ func (r *opsRepository) listHourlyMetricsRows(ctx context.Context, filter *servi
 		if platform != "" {
 			where += fmt.Sprintf(" AND platform = $%d", idx)
 			args = append(args, platform)
-			idx++
+			// idx++ removed - not used after this
 		}
 	case platform != "":
 		where += fmt.Sprintf(" AND platform = $%d AND group_id IS NULL", idx)
 		args = append(args, platform)
-		idx++
+		// idx++ removed - not used after this
 	default:
 		where += " AND platform IS NULL AND group_id IS NULL"
 	}