fix(barcode-scanning): isTorchAvailable always returning false on iOS

[sah1l]

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Summary

• On iOS, isTorchAvailable() always returned false when called outside an active scan session because it relied on cameraView?.getCaptureDevice(), which is nil when no scan is running.
• Added a fallback to query the default wide-angle camera device directly when no scan session is active, matching Android's behavior of checking hardware capabilities independently of camera session state.

Fixes #293

[robingenz]

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