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/bloc/book_details/book_details_bloc_test.dart

@@ -0,0 +1,138 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:bookshelf_flutter/bloc/book_details/book_details_bloc.dart';
+import 'package:bookshelf_flutter/bloc/book_details/book_details_event.dart';
+import 'package:bookshelf_flutter/bloc/book_details/book_details_state.dart';
+import 'package:bookshelf_flutter/models/models.dart';
+
+void main() {
+  group('BookDetailsBloc', () {
+    late BookDetailsBloc bookDetailsBloc;
+    late Book testBook;
+
+    setUp(() {
+      bookDetailsBloc = BookDetailsBloc();
+      testBook = createBook(
+        id: '1',
+        title: 'Test Book',
+        author: 'Test Author',
+        genre: 'Test Genre',
+        annotation: 'Test annotation',
+        coverUrl: 'https://example.com/cover.jpg',
+        pages: 200,
+        language: 'English',
+        publishedYear: 2020,
+        rating: 4.5,
+        status: BookStatus.reading,
+        progress: 50,
+        isFavorite: false,
+      );
+    });
+
+    tearDown(() {
+      bookDetailsBloc.close();
+    });
+
+    test('initial state is BookDetailsState.initial()', () {
+      expect(bookDetailsBloc.state, isA<BookDetailsState>());
+      expect(bookDetailsBloc.state.isLoading, true);
+    });
+
+    group('LoadBookDetails', () {
+      test('loads book details into state', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.id, testBook.id);
+        expect(bookDetailsBloc.state.book?.title, testBook.title);
+        expect(bookDetailsBloc.state.isLoading, false);
+      });
+    });
+
+    group('ToggleFavorite', () {
+      test('toggles isFavorite from false to true', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const ToggleFavorite());
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.isFavorite, true);
+      });
+
+      test('toggles isFavorite from true to false', () async {
+        final favoriteBook = testBook.copyWith(isFavorite: true);
+        bookDetailsBloc.add(LoadBookDetails(favoriteBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const ToggleFavorite());
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.isFavorite, false);
+      });
+
+      test('does nothing when no book is loaded', () async {
+        final initialFavorite = bookDetailsBloc.state.book?.isFavorite;
+        bookDetailsBloc.add(const ToggleFavorite());
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.isFavorite, initialFavorite);
+      });
+    });
+
+    group('UpdateProgress', () {
+      test('updates progress and keeps reading status', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const UpdateProgress(75));
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.progress, 75);
+        expect(bookDetailsBloc.state.book?.status, BookStatus.reading);
+      });
+
+      test('updates status to done when progress is 100', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const UpdateProgress(100));
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.progress, 100);
+        expect(bookDetailsBloc.state.book?.status, BookStatus.done);
+      });
+
+      test('does nothing when no book is loaded', () async {
+        final initialProgress = bookDetailsBloc.state.book?.progress;
+        bookDetailsBloc.add(const UpdateProgress(50));
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.progress, initialProgress);
+      });
+    });
+
+    group('UpdateStatus', () {
+      test('updates book status', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const UpdateStatus(BookStatus.done));
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.book?.status, BookStatus.done);
+      });
+    });
+
+    group('DeleteBook', () {
+      test('sets isDeleted to true', () async {
+        bookDetailsBloc.add(LoadBookDetails(testBook));
+        await Future.delayed(Duration.zero);
+
+        bookDetailsBloc.add(const DeleteBook());
+        await Future.delayed(Duration.zero);
+
+        expect(bookDetailsBloc.state.isDeleted, true);
+      });
+    });
+  });
+}