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/app_state.dart

@@ -0,0 +1,53 @@
+import 'package:equatable/equatable.dart';
+import '../models/models.dart';
+
+class AppState extends Equatable {
+  final AppScreen currentScreen;
+  final List<Book> books;
+  final Book? selectedBook;
+  final Map<String, dynamic>? prefilledData;
+  final String searchQuery;
+  final bool isLoading;
+  final String? errorMessage;
+
+  const AppState({
+    this.currentScreen = AppScreen.library,
+    this.books = const [],
+    this.selectedBook,
+    this.prefilledData,
+    this.searchQuery = '',
+    this.isLoading = false,
+    this.errorMessage,
+  });
+
+  AppState copyWith({
+    AppScreen? currentScreen,
+    List<Book>? books,
+    Book? selectedBook,
+    Map<String, dynamic>? prefilledData,
+    String? searchQuery,
+    bool? isLoading,
+    String? errorMessage,
+  }) {
+    return AppState(
+      currentScreen: currentScreen ?? this.currentScreen,
+      books: books ?? this.books,
+      selectedBook: selectedBook,
+      prefilledData: prefilledData ?? this.prefilledData,
+      searchQuery: searchQuery ?? this.searchQuery,
+      isLoading: isLoading ?? this.isLoading,
+      errorMessage: errorMessage ?? this.errorMessage,
+    );
+  }
+
+  @override
+  List<Object?> get props => [
+        currentScreen,
+        books,
+        selectedBook,
+        prefilledData,
+        searchQuery,
+        isLoading,
+        errorMessage,
+      ];
+}