The marketing team wants to identify the three highest-revenue product categories from paid orders placed through the web or app.
Only categories with at least two different customers qualify. A customer counts as one buyer per category, regardless of how many orders they placed.
Guest orders without a customer_id contribute to revenue but do not count as buyers. Orders without a recorded category are not included.
Prepare a report showing the top three qualifying categories, their number of unique buyers, and total revenue.
Ordering: Sort by revenue_usd from highest to lowest. For equal revenue, prioritize more buyers, then category alphabetically. Return at most 3 rows.