7-Day Rolling Revenue and Signups

The analytics team wants to analyze trends by creating a 7-day rolling summary of both revenue and signups for each day in the dataset. They need to see, for every day from the earliest to the latest in the daily_sales table, the sum of revenue from daily_sales and the sum of signup_count from signups for the 7-day window ending on that day (inclusive). Days with no signups should be treated as zero for signup_count.