run hard challenge every 6 hours

app.py

@@ -621,7 +621,7 @@ if __name__ == "__main__":
     scheduler = BackgroundScheduler()
     scheduler.add_job(func=backup_db, trigger="interval", seconds=600)
     scheduler.add_job(
-        func=run_summary_hard, trigger=CronTrigger(hour=8, timezone=timezone.utc)
+        func=run_summary_hard, trigger=CronTrigger(hour="2,8,14,20", timezone=timezone.utc)
     )
     # scheduler.add_job(func=run_summary_hard, trigger=CronTrigger(hour="*/1", timezone=timezone.utc))
     scheduler.start()