feat(ios): add iPad multitasking camera support

[msageryd]

Summary

Adds support for iPad Split View / Slide Over multitasking:

• Enable isMultitaskingCameraAccessEnabled on iOS 16+ devices that support it
• Add session interruption observers for AVCaptureSessionWasInterrupted
• Report session/multitasking-camera-not-supported error to JS when camera is interrupted due to videoDeviceNotAvailableWithMultipleForegroundApps
• Auto-restart camera when interruption ends (user closes other apps)

Problem

On iPad, when the app is in Split View or Slide Over with another app, the camera shows a black screen. There's no feedback to the user about why the camera isn't working.

Solution

1. For M-series iPads (M1, M2, M3, etc.): Enable isMultitaskingCameraAccessEnabled so the camera works in split view
2. For older iPads: Send a proper error (session/multitasking-camera-not-supported) to the JS side so apps can show a user-friendly message explaining the limitation

Changes

• CameraSession.swift: Added interruption observers and multitasking enable logic
• CameraError.swift: Added new SessionError.multitaskingCameraNotSupported case

Usage

Apps can handle the error in onError:

<Camera
  onError={(error) => {
    if (error.code === 'session/multitasking-camera-not-supported') {
      // Show message: "Camera cannot run in split view on this iPad"
    }
  }}
/>

Testing

Tested on:

• iPad Air 7th gen with M3 chip (iOS 18.6.2) - camera works in Split View
• iPad Air 7th gen with M3 chip (iOS 26.2) - camera works in Split View and Slide Over view
• iPad Pro 3rd gen with A12X chip (iOS 26.2) - receives session/multitasking-camera-not-supported error in Split View, camera auto-restarts when returning to full screen

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