feat(studio): iPad screenshot support + cleanup

Generalize the studio into a Platform/DeviceModel abstraction so it renders
both iPhone and iPad sets from one code path.

- Platform: per-target canvas (iPad 2064x2752), 3D model, capture sim, and
  output subfolder (iPad -> <Language>/iPad/). PLATFORM=iphone|ipad.
- DeviceModel: screen material, orientation (yaw) fix, optional glass mesh,
  graphite recolor — the per-model quirks the renderer needs.
- SceneKit renderer: auto-generates planar UVs for screen meshes that ship
  without them; textures every material matching the screen name; zFar scaled
  for large-unit models; body recolor skips the real screen material.
- iPad uses a CC BY 4.0 model (commercial-safe) with real bezel geometry;
  first-pass iPad layouts for all four screens. capture.sh is PLATFORM-aware.

Remove now-dead code: the 2D mockup fallback (ClipDeviceRenderer,
MockupGeometry), the orbit ring and binary-tunnel (superseded by the route arc
and the encryption-flow), unused DeviceModel UV/inset workarounds; refresh the
README and .gitignore to match.

packaging/apple/studio/assets/ATTRIBUTION.md

@@ -6,7 +6,12 @@
 - **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
+## ipad-pro.usdz
+- **Title:** 2018 Apple iPad Pro
+- **Author:** lazercar (Sketchfab)
+- **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 these models (or renders derived from them)
+are 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.