feat: use symbol from db when currencyFormatter does not support the currency
feat: use currencyConverter for notifications as well
fix: date comparison check on sendnotifications cronjob
feat: show timezone on sendnotification cronjob on admin page
fix: emails with encryption set to none not working without ssl
fix: error when not setting custom headers for ntfy
refactor: run linter and cleanup php files
fix: not every payment cycle was shown on the calendar
feat: also show previous payments on the calendar for the current month
