fix(security): auto-lock the lite wallet on idle

checkAutoLock() called App::lockWallet(), which early-returns without an
rpc_ handle — so lite wallets, which have no daemon, never idle-locked and
stayed unlocked indefinitely. Route lite through lockLiteWallet() instead,
which locks the backend and tears down the chat session so no decrypted
store / unlocked DB key survives the idle lock. Full-node builds keep
lite_wallet_ null, so the branch is a no-op there and behaviour is unchanged.

The idle timer (last_interaction_, reset on ImGui input at the top of
App::update()) is already build-agnostic, so no other wiring is needed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app_security.cpp

@@ -612,7 +612,12 @@ void App::checkAutoLock() {
     float elapsed = std::chrono::duration<float>(now - last_interaction_).count();
 
     if (elapsed >= (float)timeout) {
-        lockWallet();
+        // Lite has no daemon `walletlock` — App::lockWallet() early-returns without rpc_, so route
+        // lite through lockLiteWallet() (locks the backend + tears down the chat session so no
+        // decrypted store / unlocked DB key survives the idle lock). In full-node builds
+        // lite_wallet_ is always null, so this branch is a no-op and behaviour is unchanged.
+        if (lite_wallet_) lockLiteWallet();
+        else              lockWallet();
         DEBUG_LOGF("[App] Auto-locked wallet after %d seconds idle\n", timeout);
     }
 }