feat(lite): M3 — new-address generation + sync-indicator confirmation

- LiteWalletController::newAddress(shielded) runs the backend "new" command ("zs"/"R" ->
  do_new_address), parses the ["addr"] response, and returns the new address; the next
  refresh lists it. Fast (local derivation), safe on the UI thread.
- fake_lite_backend returns ["zs1fakenew"]/["R1fakenew"] for "new" by args.
- testLiteWalletControllerNewAddress covers shielded/transparent + no-wallet error.

Also confirmed (no code needed): the sync-progress indicator already works for lite —
balance_tab reads state.sync.* which M2b-3 populates. Per-address balances landed in M2.

Remaining M3 is pure UI wiring (receive_tab button -> newAddress, loading/empty states),
which isn't verifiable without a GUI session.

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

src/wallet/lite_wallet_controller.h

@@ -53,6 +53,12 @@ struct LiteWalletControllerOptions {
     bool allowBridgeCalls = true;
 };
 
+struct LiteNewAddressResult {
+    bool ok = false;
+    std::string address;
+    std::string error;
+};
+
 class LiteWalletController {
 public:
     LiteWalletController(WalletCapabilities capabilities,
@@ -92,6 +98,10 @@ public:
     // op produces a ready wallet; safe to call once.
     void startSync();
 
+    // Generate a new address (shielded if true, else transparent) via the backend. Fast (local
+    // key derivation), safe to call on the UI thread; the next refresh lists the new address.
+    LiteNewAddressResult newAddress(bool shielded);
+
     // Poll sync status + fetch balance/addresses/transactions, and apply the result into the
     // app's WalletState. Returns true if state was updated. Safe no-op when no wallet is open.
     // Synchronous (blocks on the backend); used by tests and as the worker's unit of work.