Partial refunds now stay visible in daily sales

Partially and fully refunded payments now remain part of the original gross
sales and transaction count. Refunds are shown separately and deducted once,
so the net amount reflects the money the venue actually retained.

Daily sales rows now show gross sales, refunds processed that day, and the
resulting net total. A refunded transaction also shows its original amount,
the cumulative amount refunded, and the remaining collected amount instead of
displaying only the original charge.

When money remains after a partial refund, authorized staff can issue another
refund up to that remaining balance. Fully refunded payments cannot be
refunded again.