Sale pricing for products & categories (regular + sale price, scheduling & rules)

Please add native sale pricing to Woosa for both product-level and category-level promotions, exposing regular and sale prices to the feed/sync and showing the crossed-out regular price on site.

Why: Seasonal promos (e.g., Black Friday), better UX (old vs new price), and alignment with WooCommerce core fields.

What we need:

• Product sale price + date range (start/end).

• Category discount rules (percent/fixed), with exclusions.

• Priority: product > category > global.

• Feed fields: regular_price, sale_price, on_sale, schedule.

• Scheduling by timezone, do not override existing Woo promos silently.