[FIX] product_sale_price_from_pricelist: Add last_purchase_price field to template

Added last_purchase_price computed field in product.template as an alias
to last_purchase_price_received. This field is required for compatibility
with Odoo's standard pricelist system which accesses template['last_purchase_price']
during price computation.

Fixes KeyError: 'last_purchase_price' in website shop controller.

product_sale_price_from_pricelist/models/product_template.py

@@ -55,6 +55,14 @@ class ProductTemplate(models.Model):
         store=True,
     )
 
+    # Alias for backward compatibility with pricelist base price computation
+    last_purchase_price = fields.Float(
+        string="Last Purchase Price",
+        compute="_compute_last_purchase_price",
+        search="_search_last_purchase_price",
+        store=True,
+    )
+
     @api.depends("product_variant_ids.last_purchase_price_updated")
     def _compute_last_purchase_price_updated(self):
         for template in self:
@@ -139,6 +147,15 @@ class ProductTemplate(models.Model):
             ("product_variant_ids.last_purchase_price_compute_type", operator, value)
         ]
 
+    @api.depends("last_purchase_price_received")
+    def _compute_last_purchase_price(self):
+        """Alias for backward compatibility with pricelist computations."""
+        for template in self:
+            template.last_purchase_price = template.last_purchase_price_received
+
+    def _search_last_purchase_price(self, operator, value):
+        return [("last_purchase_price_received", operator, value)]
+
     def action_update_list_price(self):
         """Delegate to product variants."""
         return self.product_variant_ids.action_update_list_price()