Fix Credo Design (AliasUsage): add aliases in lib

Add module aliases at top and use short names instead of
fully qualified nested modules across lib/.

lib/mv/authorization/checks/actor_is_system_user.ex

@@ -7,9 +7,11 @@ defmodule Mv.Authorization.Checks.ActorIsSystemUser do
   """
   use Ash.Policy.SimpleCheck
 
+  alias Mv.Helpers.SystemActor
+
   @impl true
   def describe(_opts), do: "actor is the system user"
 
   @impl true
-  def match?(actor, _context, _opts), do: Mv.Helpers.SystemActor.system_user?(actor)
+  def match?(actor, _context, _opts), do: SystemActor.system_user?(actor)
 end

lib/mv/authorization/checks/custom_field_value_create_scope.ex

@@ -22,6 +22,7 @@ defmodule Mv.Authorization.Checks.CustomFieldValueCreateScope do
     end
   """
   use Ash.Policy.Check
+  alias Mv.Authorization.Actor
   alias Mv.Authorization.PermissionSets
 
   @impl true
@@ -67,5 +68,5 @@ defmodule Mv.Authorization.Checks.CustomFieldValueCreateScope do
     end
   end
 
-  defp ensure_role_loaded(actor), do: Mv.Authorization.Actor.ensure_loaded(actor)
+  defp ensure_role_loaded(actor), do: Actor.ensure_loaded(actor)
 end

lib/mv/authorization/checks/has_permission.ex

@@ -81,6 +81,7 @@ defmodule Mv.Authorization.Checks.HasPermission do
   use Ash.Policy.Check
   require Ash.Query
   import Ash.Expr
+  alias Mv.Authorization.Actor
   alias Mv.Authorization.PermissionSets
   require Logger
 
@@ -397,6 +398,6 @@ defmodule Mv.Authorization.Checks.HasPermission do
   # Fallback: Load role if not loaded (in case on_mount didn't run)
   # Delegates to centralized Actor helper
   defp ensure_role_loaded(actor) do
-    Mv.Authorization.Actor.ensure_loaded(actor)
+    Actor.ensure_loaded(actor)
   end
 end