fix(定时轮): 初始化失败返回错误并补充单测

- NewTimingWheelService 改为返回 error，避免 panic

- ProvideTimingWheelService 透传 error 并更新 wire 生成代码

- 补充定时任务调度/取消/周期任务相关单元测试

backend/cmd/server/wire_gen.go

@@ -78,7 +78,10 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	dashboardAggregationRepository := repository.NewDashboardAggregationRepository(db)
 	dashboardStatsCache := repository.NewDashboardCache(redisClient, configConfig)
 	dashboardService := service.NewDashboardService(usageLogRepository, dashboardAggregationRepository, dashboardStatsCache, configConfig)
-	timingWheelService := service.ProvideTimingWheelService()
+	timingWheelService, err := service.ProvideTimingWheelService()
+	if err != nil {
+		return nil, err
+	}
 	dashboardAggregationService := service.ProvideDashboardAggregationService(dashboardAggregationRepository, timingWheelService, configConfig)
 	dashboardHandler := admin.NewDashboardHandler(dashboardService, dashboardAggregationService)
 	accountRepository := repository.NewAccountRepository(client, db)