feat(content_management): sort sources, topics, and countries lists by name

- When loading sources, topics, and countries for the edit headline form,
  the lists are now sorted alphabetically by name in ascending order.
- This change improves the user experience by providing a consistent and
  predictable order for these lists in the application.

Author: fulleni

lib/content_management/bloc/edit_headline/edit_headline_bloc.dart

@@ -53,9 +53,15 @@ class EditHeadlineBloc extends Bloc<EditHeadlineEvent, EditHeadlineState> {
         countriesResponse,
       ] = await Future.wait([
         _headlinesRepository.read(id: _headlineId),
-        _sourcesRepository.readAll(),
-        _topicsRepository.readAll(),
-        _countriesRepository.readAll(),
+        _sourcesRepository.readAll(
+          sort: [const SortOption('name', SortOrder.asc)],
+        ),
+        _topicsRepository.readAll(
+          sort: [const SortOption('name', SortOrder.asc)],
+        ),
+        _countriesRepository.readAll(
+          sort: [const SortOption('name', SortOrder.asc)],
+        ),
       ]);
 
       final headline = headlineResponse as Headline;