Adds an SSHClient gomobile binding so the Android app can run an SSH session over the tunnel with a PTY, exposed through a listener interface for the in-app terminal.
Server type is auto-detected from the SSH banner, which selects the auth path: JWT device-code flow, NetBird key, or a regular server (NetBird key first, then password). Host keys are verified against the peer registry for NetBird servers and trust-on-first-use for regular ones.
