fix(balance): stop the displayed balance cratering during a pending shielded send

Sending a small amount from an address holding a large balance made the displayed
balance collapse to ~0 until the tx confirmed. A shielded spend consumes the whole
source note; the change returns as a 0-confirmation note, and every balance query
used the default minconf=1 — so the spent note dropped out and the change wasn't
counted yet.

Split every balance into two views:

- DISPLAY (balance / privateBalance / transparentBalance / totalBalance) — now
  queried at minconf=0, so it INCLUDES the user's own pending change and no longer
  craters. This is what the Overview, balance tab, market portfolio and receive
  tab show. unconfirmedBalance is now populated (= total - spendable).
- SPENDABLE (new spendableBalance / spendable*Balance) — confirmed (minconf>=1),
  what z_sendmany (run at minconf=1) can actually spend. The Send form's available/
  Max/validation, the from-address selection, the drag-to-transfer dialog cap, the
  chat pay-from and the auto-shield gate all size off these, so they never offer
  0-conf change the daemon would reject.

Implementation: a single z_listunspent(0)/listunspent(0), partitioned per-note by
"confirmations">=1; z_gettotalbalance called at minconf 0 (display) and 1
(spendable); the z_getbalance fallback queries both. applyPendingSendDelta (the
optimistic post-send debit) now touches ONLY the spendable fields — debiting the
display too would re-crater it on top of the honest minconf=0 RPC. Lite mirrors
spendableBalance = balance (its per-address balance is already confirmed) so lite
sends aren't zeroed. The confirmed-only gates (seed-migration/sweep z_gettotalbalance,
sweep z_getbalance(addr,1), z_sendmany's minconf arg) are untouched.

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

src/wallet/lite_wallet_controller.cpp

@@ -139,6 +139,12 @@ void applyLiteRefreshModelToWalletState(const LiteWalletAppRefreshModel& model,
         state.transparentBalance = static_cast<double>(model.balance.transparentZatoshis) / kZatoshisPerCoin;
         state.totalBalance = static_cast<double>(model.balance.totalZatoshis) / kZatoshisPerCoin;
         state.unconfirmedBalance = static_cast<double>(model.balance.unconfirmedZatoshis) / kZatoshisPerCoin;
+        // Lite already tracks confirmed/unconfirmed itself and its per-address balances are confirmed
+        // (spendable outputs only). Mirror the aggregate spendable fields so full-node-shaped spend
+        // validation isn't zeroed on lite (the actual lite spend gate is per-address, set below).
+        state.spendablePrivateBalance = state.privateBalance;
+        state.spendableTransparentBalance = state.transparentBalance;
+        state.spendableTotalBalance = state.totalBalance;
     }
 
     if (model.hasAddresses) {
@@ -178,6 +184,7 @@ void applyLiteRefreshModelToWalletState(const LiteWalletAppRefreshModel& model,
             } else {
                 info.balance = 0.0;  // notes succeeded and address has no spendable outputs
             }
+            info.spendableBalance = info.balance;  // lite per-address balance is already confirmed/spendable
             info.type = (addr.kind == LiteWalletAppAddressKind::Shielded) ? "shielded" : "transparent";
             info.has_spending_key = addr.spendabilityKnown ? addr.spendable : true;
             if (addr.kind == LiteWalletAppAddressKind::Shielded) {