CustomField policies: actor required, no system-actor fallback, error handling

- list_required_custom_fields: require actor (two clauses, no default)
- Member validation: use context.actor only, differentiate Forbidden vs transient errors
- stream_custom_fields: log + send flash on error instead of returning []
- GlobalSettingsLive: handle_info for custom_fields_load_error, put_flash
- Seeds: use Membership.update_member with actor, format

lib/mv_web/live/custom_field_live/index_component.ex

@@ -12,6 +12,8 @@ defmodule MvWeb.CustomFieldLive.IndexComponent do
   """
   use MvWeb, :live_component
 
+  require Logger
+
   @impl true
   def render(assigns) do
     assigns = assign(assigns, :field_type_label, &MvWeb.Translations.FieldTypes.label/1)
@@ -177,10 +179,18 @@ defmodule MvWeb.CustomFieldLive.IndexComponent do
     """
   end
 
-  defp stream_custom_fields(actor) do
+  defp stream_custom_fields(actor, parent_pid) do
     case Ash.read(Mv.Membership.CustomField, actor: actor) do
-      {:ok, custom_fields} -> custom_fields
-      {:error, _} -> []
+      {:ok, custom_fields} ->
+        custom_fields
+
+      {:error, error} ->
+        Logger.warning(
+          "CustomFieldLive.IndexComponent: failed to load custom fields: #{inspect(error)}"
+        )
+
+        send(parent_pid, {:custom_fields_load_error, error})
+        []
     end
   end
 
@@ -215,7 +225,7 @@ defmodule MvWeb.CustomFieldLive.IndexComponent do
      |> assign_new(:show_delete_modal, fn -> false end)
      |> assign_new(:custom_field_to_delete, fn -> nil end)
      |> assign_new(:slug_confirmation, fn -> "" end)
-     |> stream(:custom_fields, stream_custom_fields(assigns[:actor]), reset: true)}
+     |> stream(:custom_fields, stream_custom_fields(assigns[:actor], self()), reset: true)}
   end
 
   @impl true