30-Day Rolling Conversion SQL

@Orchard Marketing Analytics needs to monitor how conversion performance changes across acquisition channels. Write a PostgreSQL query that calculates each channel's daily conversion rate and its 30-day rolling average.

Requirements

1. Aggregate multiple records for the same channel and date before calculating rates.
2. Calculate conversion rate as conversions divided by visits. Return NULL when visits are zero.
3. Calculate a calendar-based 30-day rolling average that includes the current date and the preceding 29 days for the same channel.
4. Ignore NULL daily rates when calculating the rolling average, and round both rates to four decimal places.
5. Return results ordered by channel and activity date.