feat: inline-editable prices in product mapping UI

Click any price cell (WC Standard, WC Sale, Odoo Price) to edit inline.
Enter or click away saves and syncs to the source. Escape cancels.
Validation: sale price cannot exceed standard price.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fusion-woo-odoo/fusion_woocommerce/models/woo_product_map.py

@@ -135,6 +135,26 @@ class WooProductMap(models.Model):
             'Standard price set to $%.2f' % price,
         )
 
+    def action_set_sale_price(self, price):
+        """Set the WC sale price directly."""
+        self.ensure_one()
+        if not self.instance_id:
+            return
+        client = self.instance_id._get_client()
+        # Sale price cannot exceed regular price
+        if self.woo_regular_price and price > self.woo_regular_price + 0.01:
+            raise UserError(
+                'Sale price ($%.2f) cannot exceed the standard price ($%.2f).'
+                % (price, self.woo_regular_price)
+            )
+        update_data = {'sale_price': str(price) if price > 0 else ''}
+        client.update_product(self.woo_product_id, update_data)
+        self.woo_sale_price = price
+        self.instance_id._log_sync(
+            'product', 'odoo_to_woo', self.woo_product_name, 'success',
+            'Sale price set to $%.2f' % price,
+        )
+
     # ------------------------------------------------------------------
     # Image Sync (Task 22)
     # ------------------------------------------------------------------