[Commerce] Ingest Etsy sold order items CSV export

[Nickel85]

Goal

Add an import path for Etsy sold order item CSV exports like EtsySoldOrderItems2026.csv.

Source Shape

Observed columns include:

• Sale Date
• Item Name
• Buyer
• Quantity
• Price
• Coupon Code
• Discount Amount
• Shipping Discount
• Order Shipping
• Order Sales Tax
• Item Total
• Currency
• Transaction ID
• Listing ID
• Date Paid
• Date Shipped
• Order ID
• Variations
• Order Type
• Listings Type
• Payment Type
• SKU

Acceptance Criteria

• Parses item-level Etsy sales exports without requiring the Etsy API.
• Normalizes listing ID, transaction ID, order ID, item name, quantity, price, discount, item total, and variations.
• Links item records to order-level records by Order ID when available.
• Preserves variation text such as size/full-set selections for later bundle and product analysis.
• Supports digital and physical listing types.
• Reports import counts, skipped rows, malformed rows, and duplicate rows.
• Adds validation fixtures based on representative headers from the sample export.

Out Of Scope

• Recommendation generation.
• Ad-spend ingestion.
• Bambu production mapping.