Mark the containing directory as viewed in the file tree when all its files are viewed

[delvh]

Feature Description

At the moment, Gitea highlights viewed files differently in the filetree (see screenshot 1, implemented by #24956).
However, I've noticed that the directories grab unnecessary attention when skimming through the tree to see what is reviewed and what isn't.
So, what I'm proposing to do when a file is marked as viewed:

• do what is currently done
• check for the parent if all its children have been marked as viewed
• if that's the case, mark this parent as viewed and continue with the parent of this directory

When a file is de-marked, we need to de-mark its parents as well.
It is some overhead compared to now, but I think it's worth it to allow faster skimming through the tree.

Screenshots

Current appearance

Expected appearance