feat: WC standard price + sale price with smart sync logic

- Split woo_price into woo_regular_price and woo_sale_price
- Sync to WC: if standard=0 sets regular_price, otherwise sets sale_price
- Validation: standard price cannot be less than sale price
- Both prices shown in mapping UI with sale price highlighted in green
- Refresh Prices pulls both values from WC API

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

fusion-woo-odoo/fusion_woocommerce/controllers/product_search.py

@@ -158,7 +158,8 @@ class WooProductSearchController(http.Controller):
                     'odoo_product_name': m.product_id.name if m.product_id else '',
                     'odoo_default_code': m.product_id.default_code or '' if m.product_id else '',
                     'odoo_price': m.product_id.list_price if m.product_id else 0.0,
-                    'woo_price': m.woo_price or 0.0,
+                    'woo_regular_price': m.woo_regular_price or 0.0,
+                    'woo_sale_price': m.woo_sale_price or 0.0,
                     'sync_price': m.sync_price,
                     'sync_inventory': m.sync_inventory,
                     'instance_id': m.instance_id.id if m.instance_id else False,