Order history log captures all state changes with timestamps

Without a persistent order history log, you cannot answer the questions that matter most during a dispute or refund: When did the order ship? Who changed the status? Was the cancellation before or after fulfillment? The only surviving evidence is the current status field and a single updatedAt timestamp that gets overwritten on every subsequent change. CWE-778 (Insufficient Logging) and GDPR Art. 5(1)(f) both require that processing activities are traceable and reconstructable. An updatedAt column proves nothing — it's a cursor, not a log.

Create an order_history table and write to it atomically inside the same database transaction as every status update. Use db.$transaction to guarantee both writes succeed or neither does.

// prisma/schema.prisma addition:
// model OrderHistory {
//   id         String   @id @default(cuid())
//   orderId    String
//   fromStatus String?
//   toStatus   String
//   actorId    String?
//   note       String?
//   createdAt  DateTime @default(now())
//   order      Order    @relation(fields: [orderId], references: [id])
// }

// lib/orders/state-machine.ts
await db.$transaction([
  db.orders.update({ where: { id: orderId }, data: { status: newStatus } }),
  db.orderHistory.create({
    data: { orderId, fromStatus: order.status, toStatus: newStatus, actorId, note },
  }),
])