- Implement caching methods for last weather fetch and image generation
- Adjust sleep duration in BatchGenerateWeatherArtsWorker from 10 seconds to 3 seconds
- Remove unused fields `last_weather_fetch` and `last_image_generation` from the cities table
- Add index on the weather_arts table for optimized querying
This refactor improves data retrieval performance for weather data
associated with cities. Caching reduces database load while the
worker modification allows for faster iterations in generating
weather arts without significantly impacting performance.