[Feature] on Allowance should have an option to reset the budget each x days

### Feature description

Hi, I think on Allowance should have an option to reset the budget each x days

Why?:
I'm using Alby to zap people on Snort,social client and I wouldn't like to spend more than x sats on each 30 days.
Obs. I would like too to specific the budget in fiat currency.

### Describe the solution

On Allowance should have an option to reset the budget each x days

The issue names no files, tests, or entry points. Start by locating the allowance implementation and its spending-limit flow, then clarify how interval resets and fiat-denominated budgets should work; done means the allowance can reset after a configurable number of days and support the requested budget currency.

Written by the indexing model from the issue text.