Scans every sales return whose sold device involved a trade-in. For each, shows the real cash portion vs. the trade-in (Exchange) portion of the original sale, and what was actually refunded. Rebalance Ledger is only offered when the trade-in device is no longer available to recover and more was refunded than the real cash collected. It adds one new money_transaction against account 5 (Exchange) — it never edits or deletes any existing row, and never moves real cash. Each rebalance is logged to stock_logs (action = 'EXCHANGE_RETURN_RECONCILED') so a record can never be rebalanced twice.