fix: embed CSS directly in component for defaultStyles prop

- Replace broken dynamic import('./style.css') with runtime CSS injection
- Embed complete CSS as string for reliable loading in built packages
- Add SSR safety check and duplicate loading prevention
- Version bump to 5.0.0-beta.1

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: davidguttman