Analyse BigCommerce refunds by method, channel and product

**Objective:** Analyse refunds on orders created from `{date-from}` to `{date-to}`, showing orders with refunded amounts of at least `{min-refund}` (default 0.01).

**Step 1: Refunded orders**

Call `bigcommerce-get-order` with `refunded-amount.min`, `date-created.from` and `date-created.to`.

**Step 2: Aggregate**

Total refunded vs total `total-including-tax`, refund rate, and breakdowns by `payment-method`, `channel-id` and `billing-country`.

**Step 3: Product detail**

For the 10 largest refunds, call `bigcommerce-get-order-product` with `order-id` and `refunded` set to true, to see which items were refunded.

**Step 4: Report**

Headline refund rate, the breakdown tables, then the products most often refunded and any pattern worth a follow-up.

**Rules & Guidelines:**

* This is a read-only job. Never call any `bigcommerce-*-add`, `bigcommerce-*-update` or `bigcommerce-*-delete` tool. Do not suggest that you changed anything.

**Validation:**

* If a read returns no records, say so plainly and stop; do not invent figures.
* If a result hits the maximum records limit, say the figures may be incomplete and name the filter that would narrow it.