fix: run Railpack install with sudo during remote deploy

Deploy-time Railpack install ran without sudo, so deploys to a remote
server with a non-root user (passwordless sudo) failed because the
install script could not write to /usr/local/bin ("A terminal is
required to authenticate").

Detect whether sudo is needed (root vs. passwordless-sudo user) and run
the install through it, matching the server-setup script.

Fixes #5007