Pin moves to v0.5.6, package version to 0.5.6:0.
One packaging change of its own: Games in Progress reported "seat 0" while
the game's own screens now say "Seat 1", so an administrator and a player
would have been describing different chairs. Same +1, same reason.
Verified on phoenix.local as an update from 0.5.5:0. The served client
carries all three of the release's fixes: the lobby's seat numbers go
through seatLabel, .bs-name.bs-turn has lost the font-weight that made the
current player's name unreadable at 11px, and the west-to-east seating line
is gated to Day 1 Stage 1.