Add ShopModel and integrate with ProductModel

- Created ShopModel with fields for shop name, description, and user association.
- Updated ProductModel to include a foreign key relationship with ShopModel.
- Added admin interface for ShopModel with search functionality.
- Created migrations for ShopModel and its integration with ProductModel.

backend/product/models.py

@@ -122,7 +122,7 @@ class ProductModel(models.Model):
     created_at = models.DateTimeField(auto_now_add=True, verbose_name='زمان ثبت محصول')
     category = models.ForeignKey(SubCategoryModel,  null=True, on_delete=models.SET_NULL, related_name='products', verbose_name='دسته بندی محصول')
     related_products = models.ManyToManyField('self', blank=True, verbose_name='محصولات مرتبط')
-
+    shop = models.ForeignKey('account.ShopModel', on_delete=models.CASCADE, related_name='products', verbose_name='فروشگاه', blank=True, null=True)
 
 
 
@@ -287,7 +287,6 @@ class ProductVariant(models.Model):
         verbose_name = 'تنوع محصول'
         verbose_name_plural = 'تنوع‌های محصول'
         indexes = [
-            # Existing indexes
             models.Index(fields=['product', 'price', 'created_at'], name='idx_product_price_created'),
             models.Index(fields=['in_stock', 'discount'], name='idx_stock_discount'),
             models.Index(fields=['created_at'], name='idx_created'),