feat(content_management): add archived topics bloc

- Create ArchivedTopicsBloc, ArchivedTopicsEvent, and ArchivedTopicsState classes
- Implement basic structure for handling archived topics using bloc pattern

Author: fulleni

lib/content_management/bloc/archived_topics/archived_topics_bloc.dart

@@ -0,0 +1,13 @@
+import 'package:bloc/bloc.dart';
+import 'package:equatable/equatable.dart';
+
+part 'archived_topics_event.dart';
+part 'archived_topics_state.dart';
+
+class ArchivedTopicsBloc extends Bloc<ArchivedTopicsEvent, ArchivedTopicsState> {
+  ArchivedTopicsBloc() : super(ArchivedTopicsInitial()) {
+    on<ArchivedTopicsEvent>((event, emit) {
+      // TODO: implement event handler
+    });
+  }
+}

lib/content_management/bloc/archived_topics/archived_topics_event.dart

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+part of 'archived_topics_bloc.dart';
+
+sealed class ArchivedTopicsEvent extends Equatable {
+  const ArchivedTopicsEvent();
+
+  @override
+  List<Object> get props => [];
+}

lib/content_management/bloc/archived_topics/archived_topics_state.dart

@@ -0,0 +1,10 @@
+part of 'archived_topics_bloc.dart';
+
+sealed class ArchivedTopicsState extends Equatable {
+  const ArchivedTopicsState();
+  
+  @override
+  List<Object> get props => [];
+}
+
+final class ArchivedTopicsInitial extends ArchivedTopicsState {}