feat(content): add edit category bloc

- Implemented edit category logic
- Added state management with bloc
- Handles loading, updates, submission

Author: fulleni

lib/content_management/bloc/edit_category/edit_category_bloc.dart

@@ -0,0 +1,147 @@
+import 'package:bloc/bloc.dart';
+import 'package:equatable/equatable.dart';
+import 'package:ht_data_repository/ht_data_repository.dart';
+import 'package:ht_shared/ht_shared.dart';
+
+part 'edit_category_event.dart';
+part 'edit_category_state.dart';
+
+/// A BLoC to manage the state of editing a single category.
+class EditCategoryBloc extends Bloc<EditCategoryEvent, EditCategoryState> {
+  /// {@macro edit_category_bloc}
+  EditCategoryBloc({
+    required HtDataRepository<Category> categoriesRepository,
+    required String categoryId,
+  }) : _categoriesRepository = categoriesRepository,
+       _categoryId = categoryId,
+       super(const EditCategoryState()) {
+    on<EditCategoryLoaded>(_onLoaded);
+    on<EditCategoryNameChanged>(_onNameChanged);
+    on<EditCategoryDescriptionChanged>(_onDescriptionChanged);
+    on<EditCategoryIconUrlChanged>(_onIconUrlChanged);
+    on<EditCategorySubmitted>(_onSubmitted);
+  }
+
+  final HtDataRepository<Category> _categoriesRepository;
+  final String _categoryId;
+
+  Future<void> _onLoaded(
+    EditCategoryLoaded event,
+    Emitter<EditCategoryState> emit,
+  ) async {
+    emit(state.copyWith(status: EditCategoryStatus.loading));
+    try {
+      final category = await _categoriesRepository.read(id: _categoryId);
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.initial,
+          initialCategory: category,
+          name: category.name,
+          description: category.description ?? '',
+          iconUrl: category.iconUrl ?? '',
+        ),
+      );
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+
+  void _onNameChanged(
+    EditCategoryNameChanged event,
+    Emitter<EditCategoryState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        name: event.name,
+        // Reset status to allow for re-submission after a failure.
+        status: EditCategoryStatus.initial,
+      ),
+    );
+  }
+
+  void _onDescriptionChanged(
+    EditCategoryDescriptionChanged event,
+    Emitter<EditCategoryState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        description: event.description,
+        status: EditCategoryStatus.initial,
+      ),
+    );
+  }
+
+  void _onIconUrlChanged(
+    EditCategoryIconUrlChanged event,
+    Emitter<EditCategoryState> emit,
+  ) {
+    emit(
+      state.copyWith(
+        iconUrl: event.iconUrl,
+        status: EditCategoryStatus.initial,
+      ),
+    );
+  }
+
+  Future<void> _onSubmitted(
+    EditCategorySubmitted event,
+    Emitter<EditCategoryState> emit,
+  ) async {
+    if (!state.isFormValid) return;
+
+    // Safely access the initial category to prevent null errors.
+    final initialCategory = state.initialCategory;
+    if (initialCategory == null) {
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.failure,
+          // TODO(l10n): Localize this message.
+          errorMessage: 'Cannot update: Original category data not loaded.',
+        ),
+      );
+      return;
+    }
+
+    emit(state.copyWith(status: EditCategoryStatus.submitting));
+    try {
+      // Use null for empty optional fields, which is cleaner for APIs.
+      final updatedCategory = initialCategory.copyWith(
+        name: state.name,
+        description: state.description.isNotEmpty ? state.description : null,
+        iconUrl: state.iconUrl.isNotEmpty ? state.iconUrl : null,
+      );
+
+      await _categoriesRepository.update(
+        id: _categoryId,
+        item: updatedCategory,
+      );
+      emit(state.copyWith(status: EditCategoryStatus.success));
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: EditCategoryStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+}