feat: upgrade to koa v3 and zod v4

[to-kn]

i upgraded dependencies to koa v3 and zod v4 since we ran into problems with zod v3 and zod v4 present in our codebase

Checklist

• I have ensured my pull request is not behind the main or master branch of the original repository.
• I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• I have written a commit message that passes commitlint linting.
• I have ensured that my code changes pass linting tests.
• I have ensured that my code changes pass unit tests.
• I have described my pull request and the reasons for code changes along with context if necessary.