Fixed: notification email amounts now match what customers are charged

Default notification emails could show figures that didn't match what the customer actually paid: a subtotal equal to the total with a coupon line that was never applied, or a reminder email quoting an amount different from the charge that followed it. Both were most likely on foreign-currency contracts and on subscriptions whose first order carried a discount.

Every amount is now read from the order it's actually about, in the subscription's own currency, across new-subscription confirmations, renewal reminders, payment-failure notices, and Smart Recovery emails. A coupon or discount only appears in the email when the order it describes actually used one.

Default emails also now follow Subi's brand styling consistently, alongside the amount fix.

This only affects Subi's default notification email templates; a template you've customized yourself is unaffected.