feat(fullnode): auto-reconcile wallet after bootstrap; runtime rescan for pruned nodes

A wallet bootstrapped from a snapshot keeps its wallet.dat but never rescans, so
its spent-state is stale and the first send tries to spend already-spent notes and
is rejected. The startup -rescan flag can't fix it either: the snapshot lacks the
pre-snapshot block history -rescan needs, so it errors. The working fix is a runtime
rescanblockchain RPC from a height the snapshot actually has.

- Add App::runtimeRescan(startHeight): runs rescanblockchain via the worker, drives
  the rescanning UI state, and owns completion via the RPC callback (getrescaninfo
  is unavailable on this daemon). Suppresses the per-second mining/rescan pollers
  and the Core/balance/tx refreshes while the daemon holds cs_main for the scan.
- Add App::detectLowestAvailableBlockHeight(): async binary search via getblock for
  the lowest height whose block data is on disk → the snapshot base, and whether the
  node still has full history.
- Auto-reconcile after bootstrap: both completion sites (wizard + Settings download
  dialog) mark a pending rescan; once the daemon is back up and the tip is known,
  detect the base and runtimeRescan() from it (or -rescan restart on a full node).
- Settings "Rescan Blockchain" now probes first: full-history nodes get the existing
  -rescan restart; bootstrapped/pruned nodes get a prompt pre-filled with the
  detected base height that runs the runtime rescan.

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

src/app_wizard.cpp

@@ -774,6 +774,8 @@ void App::renderFirstRunWizard() {
                     auto finalProg = bootstrap_->getProgress();
                     if (finalProg.state == util::Bootstrap::State::Completed) {
                         bootstrap_.reset();
+                        // Reconcile the preserved wallet.dat against the new chain once the daemon is up.
+                        markPostBootstrapRescanPending();
                         wizard_phase_ = WizardPhase::EncryptOffer;
                     } else {
                         wizard_phase_ = WizardPhase::BootstrapFailed;