[Enhancement] Delete media after "x" days (#160)

* [Enhancement] Adds ability to stop media from re-downloading (#159)

* Added column

* Added methods for ignoring media items from future download

* Added new deletion options to controller and UI

* Added controller actions and UI for editing a media item

* Added column to sources

* Added retention period to form

* [WIP] getting retention methods in place

* Hooked up retention worker

* Added column and UI to prevent automatic deletion

* Docs

* Removed unused backfill worker

* Added edit links to media item tabs on source view

* Clarified form wording

* Form wording (again)

README.md

@@ -48,6 +48,7 @@ If it doesn't work for your use case, please make a feature request! You can als
   - Uses a novel approach to download new content more quickly than other apps
 - Supports downloading audio content
 - Custom rules for handling YouTube Shorts and livestreams
+- Optionally automatically delete old content ([docs](https://github.com/kieraneglin/pinchflat/wiki/Automatically-Delete-Media))
 - Advanced options like setting cutoff dates and filtering by title
 - Reliable hands-off operation
 - Can pass cookies to YouTube to download your private playlists ([docs](https://github.com/kieraneglin/pinchflat/wiki/YouTube-Cookies))