Display Discount Source in Shopify Order Details

When subscription discounts are applied, the Shopify invoice shows only the final discounted price. Store owners cannot see that the discount came from the Subi subscription app, making it unclear whether the discount is from a newsletter subscription or the app. **Requested Solution:** Display discount source/reason information in Shopify order details (similar to how the Subi widget shows discount badges), so store owners can clearly understand what discount was applied and why during fulfillment.