This commit adds several missing "cascade delete" actions to relationships on database tables. This effectively fixes errors while trying to delete user accounts because of pending child records.
Additionally, the observers for applications and vacancies were removed, since they are now obsolete.
The account deletion system was also refactored.
This commit introduces a new feature where users can disable the collection and display of IP addresses. It's hardcoded in the .env config file for security reasons, and demo mode ignores this setting, because it already hides IPs by default.
