fix(lint): 修复代码格式和未使用变量问题

- 修复 ops_ws_handler.go 中的代码格式和返回值
- 移除 ops_repo_latency_histogram_buckets.go 中不必要的错误检查
- 修复 api_contract_test.go 缩进并添加运维监控配置项测试
- 移除 ops_cleanup_service.go 中未使用的变量
- 添加 ops_retry.go 中缺失的 status 字段

backend/internal/service/ops_cleanup_service.go

@@ -94,20 +94,19 @@ func (s *OpsCleanupService) Start() {
 			if parsed, err := time.LoadLocation(strings.TrimSpace(s.cfg.Timezone)); err == nil && parsed != nil {
 				loc = parsed
 			}
-		}
-
-		c := cron.New(cron.WithParser(opsCleanupCronParser), cron.WithLocation(loc))
-		id, err := c.AddFunc(schedule, func() { s.runScheduled() })
-		if err != nil {
-			log.Printf("[OpsCleanup] not started (invalid schedule=%q): %v", schedule, err)
-			return
-		}
-		s.cron = c
-		s.entryID = id
-		s.cron.Start()
-		log.Printf("[OpsCleanup] started (schedule=%q tz=%s)", schedule, loc.String())
-	})
-}
+			}
+	
+			c := cron.New(cron.WithParser(opsCleanupCronParser), cron.WithLocation(loc))
+			_, err := c.AddFunc(schedule, func() { s.runScheduled() })
+			if err != nil {
+				log.Printf("[OpsCleanup] not started (invalid schedule=%q): %v", schedule, err)
+				return
+			}
+			s.cron = c
+			s.cron.Start()
+			log.Printf("[OpsCleanup] started (schedule=%q tz=%s)", schedule, loc.String())
+		})
+	}
 
 func (s *OpsCleanupService) Stop() {
 	if s == nil {

backend/internal/service/ops_retry.go

@@ -52,6 +52,7 @@ const (
 type limitedResponseWriter struct {
 	header      http.Header
 	wroteHeader bool
+	status      int
 
 	limit        int
 	totalWritten int64