Convert js to ts files

[CarolineDenis]

From @maxpatiiuk in #4558 (comment):

After spending several hours trying to resolve the build issues from https://github.com/specify/specify7/actions/runs/7963889013/job/21740345853, I got these results:

As a workaround for privatenumber/tsx#38, converted .js files to .ts
But also, it's time for those to be TypeScript
Note, I added // @ts-nocheck to the top of the files to suppress
TypeScript errors for now, but this should be removed once we move way from Backbone
Refactored our configs to use ESM over Common JS because I wasn't able to get swc-node to work.
tsx however works fine when using "type": "module" in package.json.
And it's about time to convert to ESM anyway - while there would still be some friction expected, going forward, there > would be more friction from not using ESM than using ESM
Fix issues with Leaflet in node.js. See commit comment in 342a727

[maxpatiiuk]

This issue is redundant with #4286