The relay has minted invite codes since relay#43; the app had no door to
them. Account settings now has "Invite a friend": it asks the relay for a
code, shows it large, and shares flamenetmessenger.com/join/<code>, the
page that shows who sent it, the store buttons and the code to type if
sign-up asks for one.
InviteLink.forCode repairs what a person did to a code on the way so the
link carries what the relay hashed. MessengerApi.mintInvite posts to
account/vouch on the relay root with the app credential. RateLimited now
carries the relay's own sentence when it gave one, so "You already have 5
unused invites" reaches the screen instead of "rate limited".
Five client tests; the whole client suite is green at 469.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
