Introduces email notifications for order status changes (created, cancelled, completed, paid, missing payment, refund events) and adds corresponding HTML email templates. Refactors notification tasks to use only the order object and updates model logic to trigger notifications on relevant status changes.
Moved email templates to a unified 'email' directory and added new base, header, and footer templates for emails. Implemented notification tasks in commerce for various order and refund events, and updated Carrier model to trigger notifications on shipping state changes.
