fix(lite): rebuild controller on lite-server change (stale-settings audit HIGH)

The LiteWalletController was constructed once at App::init() with the lite
connection settings known at startup; changing the lite server in Settings
persisted to disk but never reached the live controller, so the new server had
no effect until the next launch.

Factor the construction into App::rebuildLiteWallet() and call it after a
successful server-selection save. The rebuild deliberately preserves a live
session: if a wallet is already open (and possibly mid-sync), it no-ops and the
new selection applies on the next controller build, rather than discarding the
open wallet and its uninterruptible in-flight sync.

Closes the last remaining HIGH from the session audit.

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

src/app.h

@@ -157,6 +157,9 @@ public:
     config::Settings* settings() { return settings_.get(); }
     // Lite wallet controller (non-null only in lite builds with a linked backend).
     wallet::LiteWalletController* liteWallet() { return lite_wallet_.get(); }
+    // (Re)build the lite controller from current settings so a changed lite-server selection
+    // takes effect. No-op on non-lite/unlinked builds; preserves a live wallet (see app.cpp).
+    void rebuildLiteWallet();
     WalletState& state() { return state_; }
     const WalletState& state() const { return state_; }
     const WalletState& getWalletState() const { return state_; }