SO → PO → Bill: items already exist on the Sales Order. We match bill lines to SO lines by
SKU + description, then update price only — no new items are created.
Sales Order not found on PO
Enter the Zoho Books salesorder_id to load line items and enable updates.
Bill ID not detected — load manually or fix button URL
External URL buttons must pass the bill ID in the query string, e.g. https://your-ngrok-url/index.html?bill_id=${bill.bill_id}
Match compares bill line description → SO line description (not the item catalog). Same SKU + same description = auto-match. If they differ, use Pick SO line….