Both companion relays moved to new addresses, and every
build before this one has the old relay hosts hardcoded, so
a cross-revision pairing cannot deliver pushes or, once the
old relay is retired, even connect.

Bump the companion protocol revision to 5 and raise
minimumPeer to 5 (lockstep) so the app-compatibility
handshake refuses any peer older than revision 5 with an
upgrade wall instead of letting it pair into a broken
state.