Khata: let regulars pay later

Half a kirana's trade runs on trust: regulars take what they need and settle at the end of the month. The Khata tab is that notebook, with the arithmetic done for you.

1. Add to tab when someone takes goods on credit. Enter their name (a phone number helps you tell two Rams apart), the amount, and a note like "rice, oil, dal".
2. Settle when they pay, in full or in part. Part payments are normal and the balance carries.
3. Open a name to see their whole history, every credit and every payment, with the running balance.

The tab shows total outstanding across everyone and how many names are on the book, so you know what is owed to you at a glance. Someone who has overpaid shows as in credit rather than a negative.

Khata is on by default for grocery shops. Any other shop can turn it on under Settings, "What this shop does". It is yours and your permitted staff's only, never visible to customers.