Friend invites now have a short human-readable code like SNOW-A3K9 alongside the existing token, with a migration that backfills existing rows and new endpoints to look up and accept by code. Added a tiny HTML redirect page served at /invite/:token and /party/:partyId/join so links shared in iMessage actually open something when tapped, instead of showing the raw schuss:// scheme and confusing everyone. iOS side picks up the code in AddFriendView with a monospaced input and a share sheet, and friend invite deep links finally get handled in SchussApp the same way party invites do. Also added the prod webcredentials entitlement for clerk.schuss.app and fixed the watch app's icon and background modes key, which had been set to UIBackgroundModes when watchOS wants WKBackgroundModes.

4 commits across 1 repo (schuss: 4). 14 files changed.