refactor: Replace length/1 with empty list comparison

Replace expensive length/1 calls with direct list comparison
to fix Credo warnings about performance

lib/mv_web/live/member_live/form.ex

@@ -403,7 +403,7 @@ defmodule MvWeb.MemberLive.Form do
   # Checks if form has any errors
   defp has_form_errors?(form) do
     case Map.get(form, :errors) do
-      errors when is_list(errors) and length(errors) > 0 -> true
+      errors when is_list(errors) and errors != [] -> true
       _ -> false
     end
   end

test/mv/membership/import/member_csv_test.exs

@@ -404,7 +404,7 @@ defmodule Mv.Membership.Import.MemberCSVTest do
 
       assert chunk_result.inserted == 0
       assert chunk_result.failed == 10
-      assert length(chunk_result.errors) == 0
+      assert chunk_result.errors == []
     end
 
     test "error capping with mixed success and failure" do