feat(vereinfacht): add DB schema, config and setting attributes

- Migrations: vereinfacht_contact_id on members, vereinfacht_* on settings
- Mv.Config: Vereinfacht ENV/Settings helpers, vereinfacht_configured?, contact_view_url
- Setting: vereinfacht_api_url, api_key, club_id

priv/repo/migrations/20260218185510_add_vereinfacht_contact_id_to_members.exs

@@ -0,0 +1,21 @@
+defmodule Mv.Repo.Migrations.AddVereinfachtContactIdToMembers 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(:members) do
+      add :vereinfacht_contact_id, :text
+    end
+  end
+
+  def down do
+    alter table(:members) do
+      remove :vereinfacht_contact_id
+    end
+  end
+end

priv/repo/migrations/20260218185541_add_vereinfacht_settings.exs

@@ -0,0 +1,25 @@
+defmodule Mv.Repo.Migrations.AddVereinfachtSettings 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 :vereinfacht_api_url, :text
+      add :vereinfacht_api_key, :text
+      add :vereinfacht_club_id, :text
+    end
+  end
+
+  def down do
+    alter table(:settings) do
+      remove :vereinfacht_club_id
+      remove :vereinfacht_api_key
+      remove :vereinfacht_api_url
+    end
+  end
+end