R2 lifecycle rule: delete objects > 7d unless they are the first of each month

I have a script that creates a backup of my files and databases and uploads them on R2 under this structure:

YYYY-MM-DD/databases/YYYY-MM-DD_website_backup.tar.gz
YYYY-MM-DD/websites/YYYY-MM-DD_website_backup.tar.gz

I saw that the UI offers object lifecycle rules. But instead of simply adding a rule that deletes all objects created >7 days from upload, I want to also keep all backups related to the first day of each month (YYY-MM-01).

Is there a way to achieve this through prefixes? It is not clear if prefixes can contain wildcard values or not… Thanks!