Removing a podcast deletes its DownloadedEpisodes rows but leaves the downloaded files on disk #1038

Summary

remove_podcast / remove_podcast_id / remove_podcast_by_name_url (rust-api/src/database.rs) delete DownloadedEpisodes (and Episodes) for the podcast inside a transaction, but never remove the files referenced by downloadedlocation. After an unsubscribe, the audio files stay in the downloads directory with nothing in the database pointing at them. Re-subscribing to the same feed creates new episodeids, so the old files are never matched again; with auto-download on, they get downloaded a second time.

Observed (PinePods 0.9.0, PostgreSQL)

On one instance, 50 files of 11 re-subscribed podcasts and 10 files of 5 unsubscribed podcasts were left in /opt/pinepods/downloads without any DownloadedEpisodes row (about 1 GB). Re-subscribed copies also came back with autodownload = false, so the user's auto-download setting was silently lost.

Expected

When removing a podcast, either delete the downloaded files (the per-episode delete-download path already handles files), or offer a "keep downloaded files" choice. In both cases, never leave files that nothing references.