v0.5.1 — security: the bridge only answers local clients

Web pages can no longer spend through the bridge. The bridge listens on 127.0.0.1, but a page open in your browser could still send it requests. It now refuses any request from another site, and any request whose Host is not a local name, which also blocks DNS-rebinding pages. The dashboard switches are covered too. Codex sends no Origin and works as before.