v0.47.3

Fixed

• The port-collision guard missed UDP ports — that is, every AmneziaWG port.
  docker ps --filter publish=NNN does not match a UDP publication without an
  explicit protocol, so a port held by a running 2.0 server looked free and the
  guard waved the deploy through. Caught on a live node. The check now asks for
  both NNN/udp and NNN/tcp, and refuses with a clear 409 either way.

Added

• Documented, verified rollback for 3.0 in both READMEs: what the pre-deploy
  backup covers, why installing 3.0 cannot disturb a running 2.0, and the exact
  commands to remove 3.0 entirely. Verified on a production node — after install
  and rollback the 2.0 container was byte-identical (same container ID, config
  hash, clients and handshakes).