Maintaining a whitelist in the binary does not scale and might put off
third party devs.

For a host that is not in the whitelist, we instead prompt the user if
they want to accept the connection.

Since we already run a server, we simply launch the browser on
confirmation page served by our server. It is a bit weird UX, but it
was the easiest solution I could find that works everywhere.

Alternatives considered:
- native dialogs using rfd - unfortunately does not work on macOS as
  the main process is windowless
- native dialogs using SDL: looks extremely ugly, hard to figure out deployment
- use Rust's Tauri or Qt or similar for native UIs: hard to deploy

Added basic BitBox styling. The HTML file is self contained and
only uses inline styles and inline svg graphics.