feat(fullnode): add "Repair Wallet" (-zapwallettxes=2) to Settings

When a note's stored record is corrupt or its tx isn't in the canonical chain,
z_sendmany fails to build a valid sapling spend proof even after a full -rescan,
because a plain rescan replays witnesses but keeps the existing tx/note records.
The zcashd repair for this is -zapwallettxes=2, which deletes all wallet tx/note
records and rebuilds them from the chain (keys/addresses preserved).

Adds a RepairWallet lifecycle operation that mirrors the existing -rescan plumbing
(one-shot zapOnNextStart flag on the embedded daemon; -zapwallettxes=2 implies and
supersedes -rescan), an App::repairWallet() that reuses the rescan status UI (so the
status bar + warmup-end completion detection apply), and a confirmed "Repair Wallet"
button + dialog in Settings → node maintenance (embedded daemon only).

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

src/daemon/daemon_controller.cpp

@@ -96,12 +96,23 @@ bool DaemonController::rescanOnNextStart() const
     return daemon_->rescanOnNextStart();
 }
 
+void DaemonController::setZapOnNextStart(bool enabled)
+{
+    daemon_->setZapOnNextStart(enabled);
+}
+
+bool DaemonController::zapOnNextStart() const
+{
+    return daemon_->zapOnNextStart();
+}
+
 void DaemonController::prepareLifecycleOperation(const LifecycleDecision& decision,
                                                  const config::Settings* settings)
 {
     if (settings) syncSettings(settings);
     if (decision.resetCrashCount) resetCrashCount();
     if (decision.setRescanOnNextStart) setRescanOnNextStart(true);
+    if (decision.setZapOnNextStart) setZapOnNextStart(true);
 }
 
 DaemonController::ShutdownDecision DaemonController::shutdownDecision(