chore(deps): update dependency @vitejs/plugin-react to v6

@vitejs/plugin-react@6.x requires vite@^8.0.0 as a peer dep, so
bumping the plugin alone produces ERESOLVE during npm ci in the
Dockerfile's spa-build stage. Bump vite to ^8.0.0 in lock-step and
regenerate package-lock.json.

Verified locally:
  npm ci --no-audit --no-fund -- 106 packages, 917 ms
  npm run build           -- vite 8.0.13, 41 modules, built in 351 ms
  vite.config.ts          -- no API changes; defineConfig / plugins /
                             base / build / server still valid in v8

Author: renovate[bot]