fix(createHeadlineBloc): improve error handling

- Replaced errorMessage with exception property.
- Handle unexpected errors gracefully.
- Improved error reporting clarity.

Author: fulleni

lib/content_management/bloc/create_headline/create_headline_bloc.dart

@@ -70,14 +70,14 @@ class CreateHeadlineBloc
       emit(
         state.copyWith(
           status: CreateHeadlineStatus.failure,
-          errorMessage: e.message,
+          exception: e,
         ),
       );
     } catch (e) {
       emit(
         state.copyWith(
           status: CreateHeadlineStatus.failure,
-          errorMessage: e.toString(),
+          exception: UnknownException('An unexpected error occurred: $e'),
         ),
       );
     }