🧹 chore(deps-dev): Bump happy-dom from 20.14.0 to 21.0.4 - #592

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: pnpm/action-setup@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/