simplify: dedupe boilerplate and remove dead code across all layers

lib/api/marianumconnect/queries/user_search/user_search.dart

@@ -7,14 +7,11 @@ import 'user_search_response.dart';
 class UserSearch extends MarianumConnectQuery {
   UserSearch({super.dio});
 
-  Future<UserSearchResponse> run(String query) => guard(() async {
-    final response = await dio.get<List<dynamic>>(
-      endpoint('users/search'),
+  Future<UserSearchResponse> run(String query) async => UserSearchResponse(
+    result: await getList(
+      'users/search',
+      McUserSearchResult.fromJson,
       queryParameters: {'q': query},
-    );
-    final list = response.data!
-        .map((e) => McUserSearchResult.fromJson(e as Map<String, dynamic>))
-        .toList();
-    return UserSearchResponse(result: list);
-  });
+    ),
+  );
 }