feat(frontend): make Swarm Control mobile-friendly and improve chat UI contrast

Refactor browser service for parallel worker pool and deep research capabilities. Clean up redundant directories and fix potential path issues for .browser_data.

refactor: re-org frontend folder structure to simply be 'frontend' ...

- Moved ui/client-app to frontend/

- Updated README and documentation references

- Updated docker-compose, local run scripts, and remote deploy scripts to point to new frontend location