fix: use documented nuxt dev server url to fix nuxt 4 bug (#356)

* fix: use documented nuxt dev server url

The current approach worked with nuxt 3 and nuxt 3 with `compatibilityVersion: 4`, but not the nuxt
4 RC.

This is the documented, canonical way, and it works with all versions.

Co-authored-by: Daniel Roe <daniel@roe.dev>

* fix(deps): bump nuxt and @nuxt/kit to v4

nuxt is a dev dep, @nuxt/kit breaking change is to drop nuxt v2 support, which is fine

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Co-authored-by: Daniel Roe <daniel@roe.dev>

Author: serhalp