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/scanner/scanner_bloc_test.dart

@@ -0,0 +1,82 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:bookshelf_flutter/bloc/scanner/scanner_bloc.dart';
+import 'package:bookshelf_flutter/bloc/scanner/scanner_event.dart';
+import 'package:bookshelf_flutter/bloc/scanner/scanner_state.dart';
+
+void main() {
+  group('ScannerBloc', () {
+    late ScannerBloc scannerBloc;
+
+    setUp(() {
+      scannerBloc = ScannerBloc();
+    });
+
+    tearDown(() {
+      scannerBloc.close();
+    });
+
+    test('initial state is ScannerState.initial()', () {
+      expect(scannerBloc.state, isA<ScannerState>());
+      expect(scannerBloc.state.isScanning, false);
+      expect(scannerBloc.state.isProcessing, false);
+    });
+
+    group('StartScanning', () {
+      test('sets isScanning to true and clears errors', () async {
+        scannerBloc.add(const StartScanning());
+        await Future.delayed(Duration.zero);
+
+        expect(scannerBloc.state.isScanning, true);
+        expect(scannerBloc.state.isProcessing, false);
+        expect(scannerBloc.state.errorMessage, isNull);
+      });
+    });
+
+    group('StopScanning', () {
+      test('sets isScanning to false', () async {
+        scannerBloc.add(const StartScanning());
+        await Future.delayed(Duration.zero);
+
+        scannerBloc.add(const StopScanning());
+        await Future.delayed(Duration.zero);
+
+        expect(scannerBloc.state.isScanning, false);
+      });
+    });
+
+    group('BookDetected', () {
+      test('stores detected book data and sets isProcessing to true', () async {
+        final bookData = {
+          'title': 'Detected Book',
+          'author': 'Detected Author',
+        };
+
+        scannerBloc.add(BookDetected(bookData));
+        await Future.delayed(Duration.zero);
+
+        expect(scannerBloc.state.detectedBookData, bookData);
+        expect(scannerBloc.state.isProcessing, true);
+      });
+    });
+
+    group('ClearDetectedBook', () {
+      test('clears detected book data and resets processing', () async {
+        final bookData = {
+          'title': 'Detected Book',
+          'author': 'Detected Author',
+        };
+
+        scannerBloc.add(BookDetected(bookData));
+        await Future.delayed(Duration.zero);
+
+        expect(scannerBloc.state.detectedBookData, isNotNull);
+
+        scannerBloc.add(const ClearDetectedBook());
+        await Future.delayed(Duration.zero);
+
+        expect(scannerBloc.state.detectedBookData, isNull);
+        expect(scannerBloc.state.isProcessing, false);
+      });
+    });
+  });
+}