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_event.dart

@@ -0,0 +1,20 @@
+abstract class ScannerEvent {
+  const ScannerEvent();
+}
+
+class StartScanning extends ScannerEvent {
+  const StartScanning();
+}
+
+class StopScanning extends ScannerEvent {
+  const StopScanning();
+}
+
+class BookDetected extends ScannerEvent {
+  final Map<String, dynamic> bookData;
+  const BookDetected(this.bookData);
+}
+
+class ClearDetectedBook extends ScannerEvent {
+  const ClearDetectedBook();
+}