refactor: squash migrations into single authorization domain migration

Combine initial authorization migration with UUIDv7 update into
one migration. Migration now creates roles table with UUIDv7
default and explicit on_delete: :restrict FK constraint.

priv/repo/migrations/20260106161215_add_authorization_domain.exs

@@ -13,7 +13,7 @@ defmodule Mv.Repo.Migrations.AddAuthorizationDomain do
     end
 
     create table(:roles, primary_key: false) do
-      add :id, :uuid, null: false, default: fragment("gen_random_uuid()"), primary_key: true
+      add :id, :uuid, null: false, default: fragment("uuid_generate_v7()"), primary_key: true
     end
 
     alter table(:users) do