Setting: add member_field_required and update_single_member_field

Add JSONB attribute member_field_required, migration, Change and
Membership code interface for atomic per-field required flag.

priv/repo/migrations/20260223195453_add_member_field_required_to_settings.exs

@@ -0,0 +1,21 @@
+defmodule Mv.Repo.Migrations.AddMemberFieldRequiredToSettings do
+  @moduledoc """
+  Updates resources based on their most recent snapshots.
+
+  This file was autogenerated with `mix ash_postgres.generate_migrations`
+  """
+
+  use Ecto.Migration
+
+  def up do
+    alter table(:settings) do
+      add :member_field_required, :map
+    end
+  end
+
+  def down do
+    alter table(:settings) do
+      remove :member_field_required
+    end
+  end
+end