fix: cancel stale duration check future on alarm rule REINIT

initRuleState preserved the in-flight durationCheckFuture from the previous configuration; the next matching event then tripped the defensive WARN in setDurationCheckFuture. Cancel it explicitly before signaling reevalNeeded.

application/src/main/java/org/thingsboard/server/service/cf/ctx/state/alarm/AlarmCalculatedFieldState.java

@@ -179,6 +179,7 @@ public class AlarmCalculatedFieldState extends BaseCalculatedFieldState {
             ruleState.setActive(null);
             AlarmCondition condition = rule.getCondition();
             if (condition.hasSchedule() || (condition.getType() == AlarmConditionType.DURATION && !ruleState.isEmpty())) {
+                ruleState.cancelDurationCheckFuture();
                 reevalNeeded.set(true);
             }
         }

application/src/main/java/org/thingsboard/server/service/cf/ctx/state/alarm/AlarmRuleState.java

@@ -270,6 +270,13 @@ public class AlarmRuleState {
         this.durationCheckFuture = durationCheckFuture;
     }
 
+    public void cancelDurationCheckFuture() {
+        if (durationCheckFuture != null) {
+            durationCheckFuture.cancel(true);
+            durationCheckFuture = null;
+        }
+    }
+
     public boolean isEmpty() {
         return eventCount == 0L && firstEventTs == 0L && lastCheckTs == 0L && durationCheckFuture == null;
     }