tvOS: server configuration and session can be lost after restart #64

Bug

On Apple TV, a configured Airwave installation can return to server setup after force-quitting or restarting. Reported with App Store v1.3; its exact source revision is unverified.

Reproduction and expected behavior

1. Configure the server and sign in on Apple TV.
2. Force-quit and reopen Airwave, or restart Apple TV.
3. The reported behavior is a return to setup; the expected behavior is retained server configuration and authentication. Cache eviction reproduces loss in source-level tests; the original hardware trigger was not independently captured.

Cause and proposed fix

The pinned AsyncStorage implementation stores tvOS values in purgeable caches. Failed hydration can also incorrectly route to onboarding. PR #63 moves six small session/onboarding values to an allowlisted UserDefaults Expo module, migrates surviving values, and gates routing on successful hydration. Logout retains the server; Change Server clears it; current-session 401s require login while transient failures retain state.

The implementation already existed before this issue was opened. This report documents the scope and approach for owner review; it does not imply prior owner approval. Session regressions and native checks pass, and the contributor confirms all physical Apple TV session acceptance tests pass. A new native binary is required.