12: Add grace period support for persistent alarms

src/main/tjava/com/r35157/jupiterperpsalarm/impl/ref/PriceAlarmDefinition.tjava

@@ -11,6 +11,7 @@ public record PriceAlarmDefinition(
         PriceDirection direction,
         BigDecimal target,
         AlarmTrigger trigger,
+        long triggerGracePeriodSeconds,
         AlarmSeverity severity,
         String note
 ) {
@@ -24,5 +25,11 @@ public record PriceAlarmDefinition(
         if (target.signum() < 0) {
             throw new IllegalArgumentException("Target price cannot be negative (was: " + target.signum() + ")!");
         }
+
+        if (triggerGracePeriodSeconds < 0) {
+            throw new IllegalArgumentException(
+                    "Trigger grace period cannot be negative: " + triggerGracePeriodSeconds
+            );
+        }
     }
 }