Appease clj-kondo as a linting tool

[akosiaris]

As I am familiarizing myself more with the codebase, I can't help but see the various clj-kondo warnings. This is a series of commits that mostly appease clj-kondo. Note that I haven't touch the clojurescript part of the codebase at all, I am utterly unfamiliar with Clojurescript yet. If this is deemed OK and wanted, I can look also look into adding Github Action based linting on e.g. PRs