Add About dialog, embed JS libraries, improve license notices

Browser UI:
- Add About dialog with version, author (GitHub/LinkedIn), connected
  Lisp implementation info, and Open Source Notices link
- Add hamburger menu button to access About dialog
- Embed external JS libraries: highlight.js, Vega, Vega-Lite,
  Vega-Embed, Mermaid (previously loaded from CDN)
- Add pipe separators between links for cleaner visual separation

License management:
- Generate combined OPEN-SOURCE-NOTICES.txt in Makefile (web + Lisp)
- Update CI workflow to use combined license file
- Update all installers (RPM, DEB, NSIS, WiX) for combined file
- Add WEB-LICENSES entries for newly embedded libraries

Startup banner:
- Add author credit and GitHub URL to startup banner

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>