Kotisso: Split shared expenses: flatshares, trips, separated parents

I built Kotisso after one holiday too many spent rebuilding a spreadsheet on the drive home. Three decisions shaped it. Money is stored as integer cents, and the sum of a group's balances is always exactly zero. That invariant is asserted after every write, and it caught every accounting bug I had before any of them reached a screen. The accounting is free and stays free. A free account sees fewer rows, never different numbers: expenses outside the twelve-month window still count in the balances, in the group total and in the per-category breakdown. A truncated statement would be a false statement. No bank connection. Nothing to link, nothing to leak, and it works in a night market where you type the rate you actually got and it stays frozen at that value forever. It speaks 16 languages including Arabic right to left, installs as a PWA and opens offline. Happy to answer anything, including what it does not do.