Android delegated proving times out when the transaction pane is hidden

From feedback ticket #139 (https://app.notion.com/3ae99411cf9081888cc0f331767dc167). Reported on Android.

## Symptom

Hiding the transaction pane or switching to another app caused repeated remote-prover timeouts. The retries later succeeded. When the pane remained visible, proving was reliable.

## Expected

Delegated proving and transaction tracking should continue when the app is backgrounded or the progress pane is hidden. UI lifecycle changes should not cancel, suspend, or starve the request.

## Investigation needed

Compare foreground and background behavior for the native bridge, WebView lifecycle, network access, timers, and transaction queue. Confirm whether the timeout occurs at the remote prover or because the app stops processing its response.

## Related

#419 handles general remote-prover unavailability and fallback. This issue is the Android lifecycle-dependent timeout trigger.

Feedback DB ref: ticket 139.

Investigate the native bridge and WebView lifecycle handling in the Android codebase. Look for transaction queue management and network request handling when the app is backgrounded. Compare logs or behavior between foreground and background states to identify where the timeout originates. Confirm if the issue is in request cancellation, response processing, or timer starvation.

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