feat: allow disabling registration

priv/repo/migrations/20260313140000_add_registration_enabled_to_settings.exs

@@ -0,0 +1,20 @@
+defmodule Mv.Repo.Migrations.AddRegistrationEnabledToSettings do
+  @moduledoc """
+  Adds registration_enabled flag to settings. When false, direct registration
+  via /register is disabled; sign-in and join form remain available.
+  """
+
+  use Ecto.Migration
+
+  def up do
+    alter table(:settings) do
+      add :registration_enabled, :boolean, default: true, null: false
+    end
+  end
+
+  def down do
+    alter table(:settings) do
+      remove :registration_enabled
+    end
+  end
+end