Admin notifications overview + email preferences by notification type (incl. recipients)

Create a central Notifications overview in the admin where all events converge (including new trial lesson, subscription/sub changes, payments/chargebacks, etc.). For each notification type, I want to be able to configure: on/off, send email yes/no, and who receives it (one or more email addresses/roles). Including basic management such as filters, search function, read/unread, marking as handled, and clicking through to the relevant item (trial lesson/customer/sub).