Remove paid field from members

Remove paid field from Member resource, database migration,
tests, seeds, and UI. This field is no longer needed as payment
status is now tracked via membership fee cycles.

lib/mv/constants.ex

@@ -7,7 +7,6 @@ defmodule Mv.Constants do
     :first_name,
     :last_name,
     :email,
-    :paid,
     :phone_number,
     :join_date,
     :exit_date,