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/home/home_bloc.dart

@@ -0,0 +1,22 @@
+import 'package:flutter_bloc/flutter_bloc.dart';
+import '../../models/models.dart';
+import 'home_event.dart';
+import 'home_state.dart';
+
+class HomeBloc extends Bloc<HomeEvent, HomeState> {
+  HomeBloc() : super(HomeState.initial()) {
+    on<LoadHomeData>(_onLoadHomeData);
+    on<NavigateToScreen>(_onNavigateToScreen);
+  }
+
+  void _onLoadHomeData(LoadHomeData event, Emitter<HomeState> emit) {
+    emit(state.copyWith(
+      currentScreen: AppScreen.library,
+      isLoading: false,
+    ));
+  }
+
+  void _onNavigateToScreen(NavigateToScreen event, Emitter<HomeState> emit) {
+    emit(state.copyWith(currentScreen: event.screen));
+  }
+}