Add donation support to web interface and documentation

- Added donation button to web interface navbar
- Created donation modal with PayPal, BTC, and ETH addresses
- Added copy-to-clipboard functionality for crypto addresses
- Updated README.md with donation information
- Updated DOCUMENTATION.md with donation section
- Added .gitignore to exclude build artifacts and certificates
- Simplified wsssh/wsscp command line interface (ssh/scp implicit)