Weather Report

A weather feed sends a list of dictionaries such as {"city": "Oslo", "temp": "3", "rain_mm": 1.2}. The values arrive as text, cities sometimes go missing, and rain is sometimes absent. Write summarize_readings(rows) that cleans the feed and reports on it.

Clean it in this order:

1. Turn temp into numbers, with anything unreadable becoming missing.
2. Drop every row with no city.
3. Turn rain_mm into numbers and fill the gaps with 0.

Then return {"rows": how many rows are left, "avg_temp": the mean temperature rounded to one decimal place, "wettest": the city with the most rain}. If no rows survive, every value is 0 or None. If no temperature could be read, avg_temp is None. On a tie for the most rain, the first city wins.