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/ui/windows/bootstrap_download_dialog.h

@@ -226,6 +226,8 @@ private:
         if (s_bootstrap->isDone()) {
             auto finalProg = s_bootstrap->getProgress();
             if (finalProg.state == util::Bootstrap::State::Completed) {
+                // Reconcile the preserved wallet.dat against the new chain once the daemon is back up.
+                s_app->markPostBootstrapRescanPending();
                 s_state = State::Done;
             } else {
                 s_errorMsg = finalProg.error;