Match a bank deposit to a customer payment receipt

Atomically links an inbound bank transaction to an order_payments receipt by setting bank_transactions.matched_order_payment_id and flipping reconciliation_status to 'matched'.

No GL postings occur. The GL entry (DR Bank / CR AR) was posted when the payment receipt was recorded. This operation records only the reconciliation link for the bank statement.

Guards enforced:

• Transaction must be inbound (direction='in' or NULL); outbound transactions use the AP-side matcher instead.
• Transaction must not already be matched to a customer payment.
• Payment status must be posted, partial_refund, or succeeded.
• Entity isolation: bank transaction and order payment must belong to the same entity as the API key.

Amount warning: If the absolute difference between the bank transaction amount and the payment amount exceeds $0.05, amount_warning is populated in the response (non-blocking, for operator awareness).

A.2 Multi-invoice payments: Payments where order_id IS NULL (applied across multiple invoices) are fully supported as match targets.

Idempotency: Matching an already-matched transaction to the same payment is a no-op returning the same matched: true response.