refactor(web): extract shared current_actor controller helper

lib/mv_web/controllers/controller_helpers.ex

@@ -0,0 +1,22 @@
+defmodule MvWeb.ControllerHelpers do
+  @moduledoc """
+  Shared helpers for plug-based controllers.
+
+  The LiveView equivalent lives in `MvWeb.LiveHelpers`; this module is the
+  controller-side counterpart that works on a `Plug.Conn`.
+  """
+
+  alias Mv.Authorization.Actor
+
+  @doc """
+  Returns the request actor for a controller, loaded for authorization.
+
+  Reads `:current_user` from the connection assigns and ensures it is loaded via
+  `Mv.Authorization.Actor.ensure_loaded/1`.
+  """
+  @spec current_actor(Plug.Conn.t()) :: Mv.Accounts.User.t() | nil
+  def current_actor(conn) do
+    conn.assigns[:current_user]
+    |> Actor.ensure_loaded()
+  end
+end