This commit improves the Schedules Direct poster fetching mechanism by implementing a caching strategy for SD program posters using nginx, with a 14-day cache duration. It introduces a cache-busting feature that appends a hash of the SD icon URI to the poster URL, ensuring clients receive updated artwork without stale images. Additionally, the code structure has been refined to separate poster proxy logic into dedicated utility functions, enhancing maintainability. Tests have been added to verify the correct behavior of the new caching and proxy functionalities.