chore(deps): bump vite to 8 and @sveltejs/vite-plugin-svelte to 7 (#126)

These move together: vite-plugin-svelte 7 requires vite ^8, vite 8
requires vite-plugin-svelte 7. So one PR.

Verified locally:
- npm run check: 0 errors, 0 warnings (CI gate)
- npm run build: production build green
- esbuild override pinning ^0.27.2 still resolves cleanly under vite 8

Refs encryption4all/dobby#25, #123

Co-authored-by: dobby-yivi-agent[bot] <275734547+dobby-yivi-agent[bot]@users.noreply.github.com>
Co-authored-by: Ruben Hensen <ruben.hensen@protonmail.com>

Author: dobby-coder[bot]