feat(shutdown): implement graceful shutdown for camera session

[EthanDM]

What

Fix the navigation freeze on React Navigation/Fabric by shutting the camera session down deterministically when the view unmounts.

Changes

• Add CameraSession.shutdown, which disables photo/video/audio/code-scanner/location/torch before flipping isActive = false, and clears delegates while removing outputs.
• Stop both capture sessions asynchronously during CameraSession.deinit as a backstop.
• Have CameraView call the shutdown helper on unmount/deinit, log if teardown exceeds 2 s, and guard against concurrent shutdowns.

Tested on

• iPhone 14 Pro (iOS 26.0.1) with code scanner enabled, navigating away from the camera screen (no freeze).

Related issues

• Fixes 🐛 Navigating away on React Native 0.78+, XCode 26, and React Native Vision Camera v4.7.1 freezes the app #3636

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[jkaufman]

@EthanDM Thank you for your effort on this. We’ve been testing a patch that builds on yours and would appreciate a look.

[mrousavy]

Thanks for this PR - seems like there were some issues with proper session shutdown on Fabric - I wonder why that wasn't a problem before on Paper. Maybe view caching/recycling?

Anyways - I left some review comments

[EthanDM]

Thanks for the review @mrousavy, I addressed all of the comments and retested. Still no freezes during mount/unmount.

Let me know if anything else is needed.