fix(lite): lock/unlock parity — shared attempt-lockout, immediate unlock state, no dead PIN, surfaced encrypt failure

Lite-parity audit, FIX C (gating/validation/presentation only — no encrypt/unlock/send backend call changed):
- Lite unlock went straight to the backend with no lockout. New App::unlockLiteWallet() runs the SAME
  escalating, persisted attempt-lockout as the full node (restoreLockoutState/applyUnlockFailure), wired into
  the Settings unlock, the send-time prompt and the lock screen. A wrong-passphrase failure counts; an
  already-unlocked/not-encrypted result does not.
- state_.locked is now cleared immediately on a successful unlock (the ~2s status poll lagged, so the UI
  stayed "locked" after a correct passphrase).
- PIN quick-unlock controls are hidden in lite Settings — lite has no PIN vault, so they were dead.
- A create/restore whose passphrase encryption FAILS now raises a one-shot visible error
  (takeEncryptionFailureNotice -> lite_encrypt_failed_unencrypted) instead of only a log line; the wallet is
  left open but unencrypted. Fixed the flag on BOTH the lifecycle and the direct create/restore encrypt paths.
- A background sync save is skipped while an encrypted wallet is unlocked (the backend save re-locks it),
  resuming once locked.

Compile- and unit-verified (testLiteWalletControllerLockUnlockParity covers the save-deferral + encrypt-failure
notice, run twice for the flaky guard); the lock-screen lockout/PIN-hiding UX itself is runtime/GUI-only and
not exercised here — worth a manual lite GUI pass.

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

src/ui/pages/settings_page.cpp

@@ -1708,7 +1708,11 @@ void RenderSettingsPage(App* app) {
 
                     // PIN unlock controls, trailing the auto-lock combo on the same row.
                     bool isEncryptedPIN = app->state().isEncrypted();
-                    if (isEncryptedPIN) {
+                    // Lite has no PIN quick-unlock: its unlock paths (Settings, send-time prompt) take the passphrase
+                    // directly and never consult a PIN vault, so these controls would be dead. Hide them.
+                    if (app->isLiteBuild()) {
+                        // nothing to show
+                    } else if (isEncryptedPIN) {
                         bool hasPIN = app->hasPinVault();
                         float pinBtnW = std::min(rowBtnW({TR("settings_set_pin"), TR("settings_change_pin"), TR("settings_remove_pin")}), (secColW - Layout::spacingSm()) * 0.5f);
 
@@ -2172,9 +2176,10 @@ void RenderSettingsPage(App* app) {
                                 if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_lite_unlock_pass"));
                                 ImGui::SetCursorScreenPos(ImVec2(leftX, ImGui::GetCursorScreenPos().y));
                                 if (TactileButton(TrId("lite_unlock", "LiteUnlock").c_str(), ImVec2(0, 0), S.resolveFont("button"))) {
-                                    const bool ok = app->liteWallet()->unlockWallet(s_settingsState.lite_enc_pass);
+                                    std::string unlockErr;
+                                    const bool ok = app->unlockLiteWallet(std::string(s_settingsState.lite_enc_pass), &unlockErr);
                                     sodium_memzero(s_settingsState.lite_enc_pass, sizeof(s_settingsState.lite_enc_pass));
-                                    s_settingsState.lite_encryption_status = ok ? TR("lite_wallet_unlocked") : TR("lite_unlock_failed");
+                                    s_settingsState.lite_encryption_status = ok ? std::string(TR("lite_wallet_unlocked")) : unlockErr;
                                 }
                                 if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_lite_unlock"));
                             } else {