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/book_details/book_details_state.dart

@@ -0,0 +1,44 @@
+import 'package:equatable/equatable.dart';
+import '../../models/models.dart';
+
+class BookDetailsState extends Equatable {
+  final Book? book;
+  final bool isLoading;
+  final bool isDeleted;
+  final String? errorMessage;
+
+  const BookDetailsState({
+    this.book,
+    this.isLoading = false,
+    this.isDeleted = false,
+    this.errorMessage,
+  });
+
+  factory BookDetailsState.initial() {
+    return const BookDetailsState(
+      isLoading: true,
+    );
+  }
+
+  BookDetailsState copyWith({
+    Book? book,
+    bool? isLoading,
+    bool? isDeleted,
+    String? errorMessage,
+  }) {
+    return BookDetailsState(
+      book: book ?? this.book,
+      isLoading: isLoading ?? this.isLoading,
+      isDeleted: isDeleted ?? this.isDeleted,
+      errorMessage: errorMessage ?? this.errorMessage,
+    );
+  }
+
+  @override
+  List<Object?> get props => [
+        book,
+        isLoading,
+        isDeleted,
+        errorMessage,
+      ];
+}