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>

tests/test_phase4.cpp

@@ -934,6 +934,7 @@ void testSpendableFiltering()
     addresses.push_back({"zs-low", 2.0, "shielded", true});
     addresses.push_back({"R-zero", 0.0, "transparent", true});
     addresses.push_back({"R-high", 5.0, "transparent", true});
+    for (auto& a : addresses) a.spendableBalance = a.balance;  // selection now ranks by CONFIRMED balance
 
     EXPECT_EQ(dragonx::bestSpendableAddressIndex(addresses), 3);
 
@@ -1424,10 +1425,10 @@ void testNetworkRefreshRpcCollectors()
     });
     auto core = Refresh::collectCoreRefreshResult(coreRpc);
     EXPECT_TRUE(coreRpc.methodNames() == std::vector<std::string>({
-        "z_gettotalbalance", "getblockchaininfo"
+        "z_gettotalbalance", "z_gettotalbalance", "getblockchaininfo"   // display (minconf=0) + spendable (minconf=1)
     }));
-    EXPECT_EQ(coreRpc.calls[0].params, json::array());
-    EXPECT_EQ(coreRpc.calls[1].params, json::array());
+    EXPECT_EQ(coreRpc.calls[0].params, json::array({0}));
+    EXPECT_EQ(coreRpc.calls[1].params, json::array({1}));
     EXPECT_TRUE(core.balanceOk);
     EXPECT_TRUE(core.blockchainOk);
     EXPECT_NEAR(*core.totalBalance, 4.25, 0.00000001);
@@ -1440,7 +1441,7 @@ void testNetworkRefreshRpcCollectors()
     coreFallbackRpc.addResponse("getblockchaininfo", json{{"blocks", 8}, {"headers", 9}});
     auto partialCore = Refresh::collectCoreRefreshResult(coreFallbackRpc);
     EXPECT_TRUE(coreFallbackRpc.methodNames() == std::vector<std::string>({
-        "z_gettotalbalance", "getblockchaininfo"
+        "z_gettotalbalance", "z_gettotalbalance", "getblockchaininfo"
     }));
     EXPECT_FALSE(partialCore.balanceOk);
     EXPECT_TRUE(partialCore.blockchainOk);
@@ -1566,7 +1567,7 @@ void testNetworkRefreshRpcCollectors()
     auto fallbackAddresses = Refresh::collectAddressRefreshResult(fallbackRpc);
     EXPECT_TRUE(fallbackRpc.methodNames() == std::vector<std::string>({
         "z_listaddresses", "z_validateaddress", "z_listunspent",
-        "z_getbalance", "getaddressesbyaccount", "listunspent"
+        "z_getbalance", "z_getbalance", "getaddressesbyaccount", "listunspent"   // display (minconf=0) + spendable (minconf=1)
     }));
     EXPECT_TRUE(fallbackAddresses.shieldedAddresses[0].has_spending_key);
     EXPECT_NEAR(fallbackAddresses.shieldedAddresses[0].balance, 4.75, 0.00000001);
@@ -1963,7 +1964,8 @@ void testNetworkRefreshResultModels()
     dragonx::WalletState state;
 
     auto core = Refresh::parseCoreRefreshResult(
-        json{{"private", "1.25000000"}, {"transparent", "0.50000000"}, {"total", "1.75000000"}},
+        json{{"private", "1.25000000"}, {"transparent", "0.50000000"}, {"total", "1.75000000"}},   // display (minconf=0)
+        json{{"private", "1.00000000"}, {"transparent", "0.50000000"}, {"total", "1.50000000"}},   // spendable (minconf=1)
         true,
         json{{"blocks", 100}, {"headers", 105}, {"bestblockhash", "apply-best-100"}, {"verificationprogress", 0.75},
              {"longestchain", 110}, {"notarized", 90}},
@@ -1972,6 +1974,10 @@ void testNetworkRefreshResultModels()
     EXPECT_NEAR(state.shielded_balance, 1.25, 0.00000001);
     EXPECT_NEAR(state.transparent_balance, 0.5, 0.00000001);
     EXPECT_NEAR(state.total_balance, 1.75, 0.00000001);
+    // Confirmed/spendable stays at minconf=1; unconfirmed = display total - spendable total (the pending change).
+    EXPECT_NEAR(state.spendablePrivateBalance, 1.0, 0.00000001);
+    EXPECT_NEAR(state.spendableTotalBalance, 1.5, 0.00000001);
+    EXPECT_NEAR(state.unconfirmedBalance, 0.25, 0.00000001);
     EXPECT_EQ(state.sync.blocks, 100);
     EXPECT_EQ(state.sync.headers, 105);
     EXPECT_EQ(state.sync.best_blockhash, std::string("apply-best-100"));