Commission is default for most products. Simple model: employee
rate × sale price. Override table for exceptions (consignment at 0%,
category-level adjustments). Commission snapshotted at time of sale.
Covers consignment lifecycle, settlement workflow, POS integration,
accounting journal entries (commission income vs consignment payable),
reporting, and business rules. Consignment items use account entity
for consignors (not suppliers).
Replace stripe_customer_id on account with account_processor_link
table. Update account_payment_method to use processor enum +
processor_payment_method_id instead of Stripe-specific fields.
Supports multiple simultaneous processors for migration scenarios.
