Clean up repository - remove unnecessary files

- Removed all unnecessary deployment scripts (Heroku, Docker, etc)
- Deleted redundant documentation (kept only README.md)
- Removed unused HTML files (debug, test, simple pages)
- Deleted duplicate database rules file
- Removed unused auth-secure.js
- Simplified deployment to single deploy.sh script
- Kept only files relevant to Vercel + Firebase deployment

This makes the repository cleaner and less confusing for maintenance.

Author: Archith