[Enhancement]: Add ability to detect existing podcast episodes

[hoggatt]

Describe the feature/enhancement

For one reason or another, I must have wiped all my podcasts (except one) from audiobookshelf.

The problem is that even though all my podcasts are present in the correct folder, they are not showing up in audiobookshelf even if I add the podcast back. It would be nice if audiobookshelf could detect already downloaded episodes. It doesn't have to be fancy (like detecting the shows + episodes automatically, although that would be nice), but detecting just existing episodes would be nice.

[hoggatt]

Nevermind, just found out that the Re-Scan button in the podcast edit modal does this exactly! Cool stuff. Hope this helps someone else with the same issue.