feat: use cron for monthly ZapPlanner payments

[rolznz]

Closes #1643

This way we ensure payments are made exactly monthly, both for the normal ZapPlanner app and for the support payments.

[reneaaron]

Looks good to me, although that means the payment isn't executed right after creation, right? (iirc there is some toast "Your payment is scheduled to be executed immediately")

How does that play together with the monthly budgets in Alby Hub? Is a monthly budget reset every 1st of the month? 🤔

[rolznz]

@reneaaron thanks for the review

although that means the payment isn't executed right after creation, right? (iirc there is some toast "Your payment is scheduled to be executed immediately")

Yeah, I changed it to show a different message on the toast for this case.

How does that play together with the monthly budgets in Alby Hub? Is a monthly budget reset every 1st of the month? 🤔

This exactly fixes the problem, because hub budgets are reset on the 1st of the month. Now with cron we can ensure we only make exactly one payment per month, rather than guessing by setting an interval of 31 days.

[im-adithya]

utACK