I like that you chose Sveltekit, and the project structure seems pretty good. But there's a lot to fix. The page load takes way too long (you should be using #await whenever possible), and the design is very messy.

If I may suggest, I think you should be using a UI framework. It will keep you in-line, and give you good defaults, and maybe even save you time. I feel like Carbon is a good match for this sort of app. But If you don't like it, Skeleton also seems like a good choice.

Also, imho you should be using display: flex a lot more! (or grid)

Either way, I like the initiative. I might be able to help out a little bit here and there, but I can't make any promises.

Good luck!