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_alerts.go

@@ -41,7 +41,7 @@ ORDER BY id DESC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	out := []*service.OpsAlertRule{}
 	for rows.Next() {
@@ -361,7 +361,7 @@ LIMIT ` + limitArg
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	out := []*service.OpsAlertEvent{}
 	for rows.Next() {