fix(scheduler): 修复定时任务固定频率调度时间计算问题

- 在固定频率调度中清除毫秒精度并增加一秒延迟
- 修正了从指定时间开始的触发间隔计算逻辑
- 避免了时间计算中的毫秒误差累积问题

xxl-job-admin/src/main/java/com/xxl/job/admin/scheduler/type/strategy/FixRateScheduleType.java

@@ -2,6 +2,7 @@ package com.xxl.job.admin.scheduler.type.strategy;
 
 import com.xxl.job.admin.model.XxlJobInfo;
 import com.xxl.job.admin.scheduler.type.ScheduleType;
+import com.xxl.tool.core.DateTool;
 
 import java.util.Date;
 
@@ -15,7 +16,8 @@ public class FixRateScheduleType extends ScheduleType {
             // fix rate delay, after last-trigger-time
             return nextTriggerTime;
         } else {
-            // fix rate delay, after fromTime
+            // fix rate delay, after fromTime (clear ms, second +1)
+            fromTime = DateTool.setMilliseconds(DateTool.addSeconds(fromTime, 1), 0);
             return new Date(fromTime.getTime() + Long.parseLong(jobInfo.getScheduleConf()) * 1000L);
         }
     }