feat(studio): native SwiftUI + SceneKit App Store screenshot pipeline

Replace the Typst/ImageMagick studio with a SwiftPM executable that composes
each marketing screen as a SwiftUI view and renders it headlessly via
ImageRenderer to exact 1284x2778 PNGs.

- Devices are a real iPhone 17 Pro Max .usdz textured + posed in SceneKit
  (graphite body, studio IBL); screen curvature/bezel are the model's geometry.
- Per-screen layouts (pose, globe, route arc, encryption flow) in ScreenSpec.
- send-anywhere: globe + Paris->LA route arc; uses the app's share screen.
- stay-private: converging beams -> glowing padlock -> binary protection stream,
  with localized CHIFFREMENT/PROTECTION banners and an auto-sizing header panel.
- Captions auto-shrink per locale (ViewThatFits) so long translations never clip.
- Screenshots are transient (generated/shots, git-ignored), captured per locale;
  generate.sh does capture + composite in one shot.
- Commit the .usdz model (CC BY 4.0, see assets/ATTRIBUTION.md) and globe asset.
- Remove the superseded Typst pipeline (screens.typ, build.sh, frame.sh, warp.sh).

packaging/apple/studio/assets/ATTRIBUTION.md

@@ -0,0 +1,12 @@
+# Third-party asset attributions
+
+## iphone-17-pro-max.usdz
+- **Title:** iphone 17 pro max silver
+- **Author:** TechFreak (Sketchfab)
+- **Source:** https://sketchfab.com/3d-models/iphone-17-pro-max-silver-9dbfe0d846f341bf9fc501a854f5de1a
+- **License:** Creative Commons Attribution 4.0 (CC BY 4.0) — https://creativecommons.org/licenses/by/4.0/
+
+CC BY 4.0 requires visible credit wherever this model (or a render derived from it)
+is published. The App Store screenshots produced by this studio are derivatives, so
+keep this attribution with the project. If a suitable place exists (e.g. the app's
+acknowledgements / licenses screen), surface the credit there as well.