feat(headlines-search): add default sort by updatedAt in search and load more

- Add sort parameter to readHeadlinesByTerm and readAll calls
- Set sort order to descending (newest first)
- Update affects both initial search and load more operations

Author: fulleni

lib/headlines-search/bloc/headlines_search_bloc.dart

@@ -92,6 +92,7 @@ class HeadlinesSearchBloc
                   limit: _limit,
                   cursor: successState.cursor,
                 ),
+                sort: [const SortOption('updatedAt', SortOrder.desc)],
               );
               // Cast to List<Headline> for the injector
               final headlines = response.items.cast<Headline>();
@@ -202,6 +203,7 @@ class HeadlinesSearchBloc
           rawResponse = await _headlinesRepository.readAll(
             filter: {'q': searchTerm},
             pagination: const PaginationOptions(limit: _limit),
+            sort: [const SortOption('updatedAt', SortOrder.desc)],
           );
           final headlines = rawResponse.items.cast<Headline>();
           final currentUser = _appBloc.state.user;