Automatically remove expired join request quizzes

[shahriaarrr]

fixed #11 :

• Added a cleanup_old_quizzes method to delete expired quizzes from the KV store.
• Introduced start_cleanup_task to run periodic cleanup tasks in the background.
• Configured quiz expiration to be managed independently and seamlessly.

[shahriaarrr]

@amiremohamadi

[shahriaarrr]

now i should think about it :**)

[amiremohamadi]

cf workers resources are limited so we can't rely on common approaches like spawning threads and sleeping. i recommend not to use ai for this issue as it might confuse you a little.

[amiremohamadi]

these are the potential approaches we can try:

• check if there's a way to pass callbacks to kv expired entries
• using cf queues and deliveryDelay (not sure, probably only available on paid plans)
• using cf cron triggers

[amiremohamadi]

i'm closing this as it's fixed in #23