Migrate radio buttons from GOV.UK to USWDS

- Replace .multiple-choice with .usa-radio classes
- Update radio templates to use USWDS patterns
- Remove GOV.UK dependencies from radio components
- Convert nested lists to flat divs with USWDS margin utilities
- Update tests to use new radio classes

tests/app/main/views/test_add_service.py

@@ -54,7 +54,7 @@ def test_get_should_not_render_radios_if_org_type_known(
     page = client_request.get("main.add_service")
     assert page.select_one("h1").text.strip() == "About your service"
     assert page.select_one("input[name=name]").get("value") is None
-    assert not page.select(".multiple-choice")
+    assert not page.select(".usa-radio")
 
 
 def test_show_different_page_if_user_org_type_is_local(