Attempt at Vue 3 migration

@TimeToBuildBob see your comment here:

> Submitted PR #771 to reduce vulnerabilities via npm overrides (37 → 32).
>
> The remaining 32 vulnerabilities are all rooted in the Vue 2 ecosystem (vue 2.x is EOL) — they cannot be resolved without a Vue 3 migration. The fixable transitive deps (minimatch, webpack-dev-server) are now overridden to patched versions.
>
> Previously PR #762 also fixed some (qs, babel).

_Originally posted by @TimeToBuildBob in https://github.com/ActivityWatch/aw-webui/issues/581#issuecomment-3971271220_

There should also be a separate issue (and even old PR?) about previous attempts/analysis at Vue 3 migration. Review and make a new attempt.