[Feature Request] Add a button to recheck downloads

[akabhirav]

What feature should be added to Suwayomi?

Add a button in settings, perhaps in the downloads section that forces Tachidesk to recheck all files/folders for downloaded content.

Why/Project's Benefit/Existing Problem

This will allow moving backups from one installation to another easily. This will also help users rehcheck and save themselves from downloading multiple entries if they already have them. I am not able to reproduce it consistently but this has happened before where some downloads are marked as undownloaded but the files are still there

[Robonau]

if the files are already there and you click download it wont actually download the files
it will just check it has the correct amount of pages and then set it as downloaded
(if the page numbers are different then it will re-download them)

so you aren't re-downloading already downloaded chapters

[schroda]

#732