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/wishlist/wishlist_event.dart

@@ -0,0 +1,22 @@
+abstract class WishlistEvent {
+  const WishlistEvent();
+}
+
+class LoadWishlist extends WishlistEvent {
+  const LoadWishlist();
+}
+
+class RemoveFromWishlist extends WishlistEvent {
+  final String bookId;
+  const RemoveFromWishlist(this.bookId);
+}
+
+class SearchWishlist extends WishlistEvent {
+  final String query;
+  const SearchWishlist(this.query);
+}
+
+class MoveToLibrary extends WishlistEvent {
+  final String bookId;
+  const MoveToLibrary(this.bookId);
+}