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/settings/settings_state.dart

@@ -0,0 +1,53 @@
+import 'package:equatable/equatable.dart';
+
+class SettingsState extends Equatable {
+  final bool isDarkMode;
+  final String language;
+  final bool notificationsEnabled;
+  final bool dataCleared;
+  final bool isLoading;
+  final String? errorMessage;
+
+  const SettingsState({
+    this.isDarkMode = false,
+    this.language = 'English',
+    this.notificationsEnabled = true,
+    this.dataCleared = false,
+    this.isLoading = false,
+    this.errorMessage,
+  });
+
+  factory SettingsState.initial() {
+    return const SettingsState(
+      isLoading: true,
+    );
+  }
+
+  SettingsState copyWith({
+    bool? isDarkMode,
+    String? language,
+    bool? notificationsEnabled,
+    bool? dataCleared,
+    bool? isLoading,
+    String? errorMessage,
+  }) {
+    return SettingsState(
+      isDarkMode: isDarkMode ?? this.isDarkMode,
+      language: language ?? this.language,
+      notificationsEnabled: notificationsEnabled ?? this.notificationsEnabled,
+      dataCleared: dataCleared ?? this.dataCleared,
+      isLoading: isLoading ?? this.isLoading,
+      errorMessage: errorMessage ?? this.errorMessage,
+    );
+  }
+
+  @override
+  List<Object?> get props => [
+        isDarkMode,
+        language,
+        notificationsEnabled,
+        dataCleared,
+        isLoading,
+        errorMessage,
+      ];
+}