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/scanner/scanner_bloc.dart

@@ -0,0 +1,40 @@
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'scanner_event.dart';
+import 'scanner_state.dart';
+
+class ScannerBloc extends Bloc<ScannerEvent, ScannerState> {
+  ScannerBloc() : super(ScannerState.initial()) {
+    on<StartScanning>(_onStartScanning);
+    on<StopScanning>(_onStopScanning);
+    on<BookDetected>(_onBookDetected);
+    on<ClearDetectedBook>(_onClearDetectedBook);
+  }
+
+  void _onStartScanning(StartScanning event, Emitter<ScannerState> emit) {
+    emit(state.copyWith(
+      isScanning: true,
+      isProcessing: false,
+      errorMessage: null,
+    ));
+  }
+
+  void _onStopScanning(StopScanning event, Emitter<ScannerState> emit) {
+    emit(state.copyWith(isScanning: false));
+  }
+
+  void _onBookDetected(BookDetected event, Emitter<ScannerState> emit) {
+    emit(state.copyWith(
+      detectedBookData: event.bookData,
+      isProcessing: true,
+      isScanning: false,
+    ));
+  }
+
+  void _onClearDetectedBook(ClearDetectedBook event, Emitter<ScannerState> emit) {
+    emit(state.copyWith(
+      isScanning: false,
+      clearDetectedBookData: true,
+      isProcessing: false,
+    ));
+  }
+}