Deleting all downloaded chapters doesn't reduce disk usage to 0B.

[MariusAlbrecht]

Brief summary

When downloading chapters kotatsu creates index.json and cover.* (one of multiple image formats) metadata files alongside the *.cbz files representing the actual chapters. These do not get deleted when the user deletes all downloaded chapters through the app and can only be removed manually using a file management app. I expect the app to clean up those files, especially when their disk usage is shown in the UI.

I think deleting them when the last downloaded chapter gets deleted is best.
An alternative would be to just add a button and let people do it manually in the app. That button could be placed in the "Saved manga" popup next to the "Delete read chapters" button:

Steps to reproduce

1. download a chapter
2. delete it again
3. see a few kB of disk usage in the app
4. see cover image and index json files in the respective directory

Kotatsu version

7.7.4

Android version

12

Device

OnePlus 7 Pro

Acknowledgements

• This is not a duplicate of an existing issue. Please look through the list of open issues before creating a new one.
• This is not an issue with a specific manga source. Otherwise, you have to open an issue in the parsers repository.