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/test/widget_test.dart

@@ -0,0 +1,21 @@
+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility in the flutter_test package. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:bookshelf_flutter/main.dart';
+
+void main() {
+  testWidgets('App starts successfully', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(const BookshelfApp());
+
+    // Verify that the app builds successfully
+    expect(find.byType(MaterialApp), findsOneWidget);
+  });
+}