Capture Camera & Photos

Background: Native [platform] app, [SwiftUI / Compose]. The feature:
[take a photo / pick from library / scan a document / record video].
What happens to the media after: [upload / store locally / process].

Use case: Implement camera capture and/or photo-library selection
idiomatically and privacy-respectfully.

Implementation details:
- iOS: PhotosPicker for library selection (no permission needed),
  AVFoundation or UIImagePickerController for capture; handle limited
  library access. Android: Photo Picker (no permission), CameraX or the
  camera intent for capture.
- Permission handling only where actually required (see 7.1)
- Image handling after capture: orientation/EXIF, downscaling before
  upload, memory pressure with large images
- Loading state and cancellation
- Saving back to the library if needed

Layer & dependencies: Captured media flows into the data layer for upload/
storage; the UI just presents the picker/capture and a preview.

Deliverable: The capture/selection implementation, the post-capture
processing (orientation + downscaling), the permission handling for the
chosen path, and the memory-safe handling of large images.