refactor: create separate BLoCs for each screen with comprehensive tests

- Created 8 separate BLoCs (Home, Library, BookDetails, AddBook, Scanner, Categories, Wishlist, Settings)
- Each BLoC has its own event, state, and bloc files
- Added 70 comprehensive tests covering all BLoC functionality
- All tests passing (70/70)
- Fixed linting issues and updated deprecated APIs
- Improved code organization and maintainability

bookshelf_flutter/lib/bloc/settings/settings_bloc.dart

@@ -0,0 +1,39 @@
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'settings_event.dart';
+import 'settings_state.dart';
+
+class SettingsBloc extends Bloc<SettingsEvent, SettingsState> {
+  SettingsBloc() : super(SettingsState.initial()) {
+    on<LoadSettings>(_onLoadSettings);
+    on<UpdateTheme>(_onUpdateTheme);
+    on<UpdateLanguage>(_onUpdateLanguage);
+    on<ToggleNotifications>(_onToggleNotifications);
+    on<ClearData>(_onClearData);
+  }
+
+  void _onLoadSettings(LoadSettings event, Emitter<SettingsState> emit) {
+    emit(state.copyWith(
+      isDarkMode: false,
+      language: 'English',
+      notificationsEnabled: true,
+      isLoading: false,
+    ));
+  }
+
+  void _onUpdateTheme(UpdateTheme event, Emitter<SettingsState> emit) {
+    emit(state.copyWith(isDarkMode: event.isDarkMode));
+  }
+
+  void _onUpdateLanguage(UpdateLanguage event, Emitter<SettingsState> emit) {
+    emit(state.copyWith(language: event.language));
+  }
+
+  void _onToggleNotifications(
+      ToggleNotifications event, Emitter<SettingsState> emit) {
+    emit(state.copyWith(notificationsEnabled: !state.notificationsEnabled));
+  }
+
+  void _onClearData(ClearData event, Emitter<SettingsState> emit) {
+    emit(state.copyWith(dataCleared: true));
+  }
+}