fix(rpc): run rescans and key imports without the 30 s timeout

A rescan or key import holds the node's cs_main for the whole wallet
scan. On the shared clients it hit the 30 s curl timeout, reported a
failure that wasn't one, abandoned a daemon RPC slot and flipped the app
into "node busy".

- One long wallet RPC at a time (rescan, importprivkey, importaddress,
  importwallet, z_importkey, z_importviewingkey, z_importwallet) runs on
  its own ungated client with no client timeout (rpc/long_call_lane.h).
  It can be aborted from any thread, and an abort is never lost, even
  one that lands before the client opens.
- The GUI rescan, key import and sweep use it. The sweep's fund-moving
  body is unchanged; only the client it calls differs. runtimeRescan()
  returns bool, and a refused post-bootstrap reconcile stays armed.
- The console routes rescan and the import commands through the lane;
  its input stays usable meanwhile, and a refusal is printed like any
  other result. RPCClient gains callRaw(.., timeoutSec).
- Restart, wallet switch, delete-chain, bootstrap (now also from
  Settings) and the other node-stopping flows are refused while it runs,
  with a message saying a key import or rescan is still running; quit
  asks for confirmation. The lane is aborted at quit.
- A second import or rescan is refused before the key is copied anywhere.
  An import cut off after the request reached the node (a lost reply,
  or a proxy's 502/504 while the node still imports) says the key may
  already be in the wallet and to run Settings -> Rescan. Only the
  node's own HTTP-layer refusals (401, 503, work queue full, unhandled
  request) say that the key was not imported. A pure
  classifyLongCallCutOff() makes that choice.
- New strings in all 8 languages; console results stay English.

Tests: the long-method list and the console's routing; one lane at a
time; an abort lands whether it comes before the client opens or during
the call; a call with no client timeout outlasts a 3 s scan, where a 1 s
gated client times out and marks the node busy; classifyLongCallCutOff()
for every failure kind with and without a sent request, and from raw
HTTP replies (502, 504, a plain 500 -> cut off; 401, 503, queue full,
unhandled -> refused).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/windows/bootstrap_download_dialog.h

@@ -299,6 +299,8 @@ private:
     // ---- Shared: kick off download ----
     static void startDownload(const std::string& url) {
         if (!s_app || !s_app->supportsFullNodeLifecycleActions()) return;
+        // It stops the node first: not while it is busy or running a key import / rescan (as the wizard's bootstrap).
+        if (s_app->refuseIfNodeBusy()) return;
         s_wasDaemonRunning = s_app->stopDaemonForBootstrap();
         s_app->setBootstrapDownloading(true);
         s_bootstrap = std::make_unique<util::Bootstrap>();