feat(lite): async + failover for Settings-page create/open/restore

The Settings page drove the controller's synchronous createWallet/openWallet/
restoreWallet, which blocks the UI thread on the (often flaky) lightwalletd and
gives up after the first server. Add a generic async lifecycle path that mirrors
the async-open failover but carries the full request (passphrase, restore seed/
birthday/account/overwrite):

  - beginCreateWalletAsync / beginOpenWalletAsync / beginRestoreWalletAsync run
    on a detached thread that builds its OWN local LiteWalletLifecycleService
    from captured value copies + the shared bridge (never `this`, so it can
    safely outlive the controller). Each request type's serverUrl override field
    feeds the failover: try the preferred server, then every other usable
    default; stop on the first ready wallet or a structural block; keep the
    preferred server's error on total failure. The request's secrets are wiped
    once the attempt finishes.
  - pumpLifecycleResult() finalizes on the main thread (flip walletOpen, persist,
    start sync) and caches the result for the UI; wired into App::update next to
    pumpAsyncOpen(). beginAsyncLifecycle() now also yields to an in-flight
    lifecycle request so the auto-open loop can't race it on the same bridge.
  - settings_page kicks off the async op, disables the button while in flight,
    and polls the cached result each frame for the status/summary.

Tests: testLiteWalletControllerAsyncLifecycleFailover covers async create (with
passphrase) and restore failing over preferred->fallback, plus all-servers-down.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app.cpp

@@ -486,6 +486,8 @@ void App::update()
     if (lite_wallet_) {
         // Finalize any completed async open on the main thread (flips walletOpen / surfaces failure).
         lite_wallet_->pumpAsyncOpen();
+        // Likewise finalize any completed async lifecycle request (Settings-page create/open/restore).
+        lite_wallet_->pumpLifecycleResult();
 
         // Auto-open an existing wallet asynchronously with server failover (initialize_existing
         // needs no passphrase — it just loads the file and contacts the server). Running it off