feat: add rows count (broken), fix: bug with low stock items

lib/services/product_service.dart

@@ -4,6 +4,13 @@ import 'package:uuid/uuid.dart';
 import '../database/app_database.dart';
 import '../models/product.dart';
 
+class InsufficientStockException implements Exception {
+  const InsufficientStockException();
+
+  @override
+  String toString() => 'Not enough stock';
+}
+
 abstract class ProductService {
   Future<List<Product>> getProducts();
 
@@ -130,7 +137,7 @@ class DriftProductService implements ProductService {
     }
 
     if (product.stockQuantity < amount) {
-      throw Exception('Not enough stock');
+      throw const InsufficientStockException();
     }
 
     await updateProduct(