Fix import paths and test issues

- Fixed test file import paths to point to correct Bloc file locations
- Fixed Bloc file import paths for models (../../../models/models.dart)
- Added explicit type annotations to resolve null safety warnings
- Fixed null safety issues in wishlist_bloc_test.dart
- All 70 tests now passing

bookshelf_flutter/lib/models/category.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+
+// Category record - using Dart records as data classes
+typedef Category = ({
+  String id,
+  String name,
+  int count,
+  IconData icon,
+  String colorClass,
+});
+
+// Helper function to create a Category record
+Category createCategory({
+  required String id,
+  required String name,
+  required int count,
+  required IconData icon,
+  required String colorClass,
+}) {
+  return (
+    id: id,
+    name: name,
+    count: count,
+    icon: icon,
+    colorClass: colorClass,
+  );
+}