v0.5.3: first run lands in a room, pastes arrive whole

Install or upgrade: pipx install quorus-ai / pipx upgrade quorus-ai

Fixed

• The first run ended on the hub home with no room open, so the first thing a new user typed
  went nowhere and @-complete found no one. It now lands inside #general. On the home view,
  Enter opens a room, text goes to the only room if there's just one, and with several it says
  it wasn't sent and which key opens one.
• The banner showed v0.5.0 whatever was installed; it shows the installed version.
• Pasting into the chat composer lost text: the rest of a paste waited until the next key,
  and a paste starting with @ stopped at the mention picker, so nothing was sent. Pastes
  now arrive whole.
• The @ picker labelled opencode agents "(human)".
• quorus relay --host 0.0.0.0 started a second relay next to the one your first quorus run
  started on 127.0.0.1:8080: on macOS both bound the port and wrote the same state file, and on
  Linux it failed to start. It now refuses while a relay answers on that port, and --replace
  stops the one quorus started (and only that one) first.
• "default" could be chosen as your name in the first-run wizard and quorus init, but
  quorus agent add refuses it, so that user could never add an agent. Both now refuse it.
• The relay couldn't use a postgres:// DATABASE_URL, which is what fly postgres attach sets.
• The README and several CLI and relay hints still showed the secret on the command line
  (--secret <s>); they all use --secret - now.

Added

• docs/deployment.md: how to share a relay with teammates or agents on other machines (your
  LAN, Tailscale, a VPS, Docker, Fly.io, Railway, Render), each with its commands, settings,
  HTTPS and whether it needs Postgres and Redis, and labelled by how far it's been tested.
  The README links it, and a test fails if a README link points at a missing file.