Update and enforce eslint

[Arnei]

Updates eslint to major version 9 and removes other eslint dependencies that are obsolete. Furthermore, adds typescript and eslint checks to the build command, so that warnings and errors must be addressed. Finally, makes the minimum amount of code changes for this to build. Currently ignored eslint rules may be enabled by subsequent commits/pull requests.

[github-actions]

This pull request is deployed at test.editor.opencast.org/1558/2025-02-25_11-34-43/ .
It might take a few minutes for it to become available.

[gregorydlogan]

So, I'm thinking that #1134 is related here. Can we enforce the tabs vs spaces debate here too? Sounds like everything else (editor, tobira, OC itself) is all spaces, so enforcing a spaces change with this might make sense.

[Arnei]

I don't see how that PR is related at all, maybe you got the wrong number?

Also this PR enforces the no-tabs eslint rule again, which enforces using spaces for indentation (unless people try using some other unholy whitespace character for indentation I guess).

[owi92]

lgtm. @gregorydlogan, I'm also a little puzzled by that linked issue 😄
Feel free to have another look at this, but otherwise I'd say this can be merged.

[gregorydlogan]

Yep, that was meant to be opencast/opencast-admin-interface#1134. As long as we're consistent tabs vs spaces wise I'm happy.