Park Hide & Seek iOS: real character models (USDZ) instead of boxes #2916

For the builder Mac (64 GB, full Xcode). Follow-up to the offline spike (#2897, merged in #2909).

People in the iOS client are boxes. Turn apps/park-hide-seek/public/models/characters.glb into USDZ with bun run usdz park-hide-seek (#2890, needs Blender), bundle it in apps/park-hide-seek/ios/App, and have Scene3D.person(...) in WorldView.swift load it, with outfits from each player's Look. Joints can stay rigid.

Done when: in the simulator, offline and online, other players show as the character model in their Look.