Build a churn risk report. For each customer, compute: days since last order (from '2025-01-01'), total orders, average order value, and days between their first and last order. Assign risk: 'High' if no order in 90+ days, 'Medium' if 60-89 days, 'Low' otherwise. Show customer_id, first_name, last_name, total_orders, avg_order_value (rounded to 2), days_since_last_order, and risk_level. Sort by days_since_last_order descending.