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/screens/home_screen.dart

@@ -0,0 +1,68 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import '../bloc/app_bloc.dart';
+import '../bloc/app_state.dart';
+import '../models/models.dart';
+import 'library_screen.dart';
+import 'categories_screen.dart';
+import 'book_details_screen.dart';
+import 'add_book_screen.dart';
+import 'scanner_screen.dart';
+import 'wishlist_screen.dart';
+import 'settings_screen.dart';
+import '../widgets/bottom_nav.dart';
+
+class HomeScreen extends StatelessWidget {
+  const HomeScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: BlocBuilder<AppBloc, AppState>(
+        builder: (context, state) {
+          final currentScreen = state.currentScreen;
+          final hideNav = [
+            AppScreen.scanner,
+            AppScreen.details,
+            AppScreen.addBook,
+          ].contains(currentScreen);
+
+          return Stack(
+            children: [
+              _buildScreen(context, state),
+              if (!hideNav)
+                Positioned(
+                  left: 0,
+                  right: 0,
+                  bottom: 0,
+                  child: BottomNav(currentScreen: currentScreen),
+                ),
+            ],
+          );
+        },
+      ),
+    );
+  }
+
+  Widget _buildScreen(BuildContext context, AppState state) {
+    switch (state.currentScreen) {
+      case AppScreen.library:
+        return const LibraryScreen();
+      case AppScreen.categories:
+        return const CategoriesScreen();
+      case AppScreen.wishlist:
+        return const WishlistScreen();
+      case AppScreen.settings:
+        return const SettingsScreen();
+      case AppScreen.details:
+        if (state.selectedBook == null) return const SizedBox();
+        return BookDetailsScreen(book: state.selectedBook!);
+      case AppScreen.addBook:
+        return AddBookScreen(
+          initialData: state.selectedBook ?? state.prefilledData,
+        );
+      case AppScreen.scanner:
+        return const ScannerScreen();
+    }
+  }
+}