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/util/i18n.cpp

@@ -635,6 +635,15 @@ void I18n::loadBuiltinEnglish()
         strings_["appx_daemon_reinstall_node_busy"] = "The node is still running, so the daemon was not reinstalled. Try again once it has stopped.";
         strings_["appx_node_busy_try_later"] = "The node is busy finishing a long task (such as rebuilding note witnesses). Try again when it is done; stopping it now could make it start that work over.";
         strings_["appx_node_not_stopped"] = "The node didn't stop in time, so nothing was changed. Try again in a few minutes.";
+        // Long wallet RPCs: one key import or rescan at a time, refusals and the quit prompt (C61)
+        strings_["appx_wallet_op_running"] = "A key import or rescan is still running. Try again when it finishes.";
+        strings_["appx_wallet_op_shutting_down"] = "The wallet is shutting down.";
+        strings_["appx_wallet_op_node_busy"] = "The node is busy and not answering. Try the import or rescan again when it finishes.";
+        strings_["appx_import_cancelled"] = "Cancelled: the node may still be scanning. If the key's funds don't appear, run Settings → Rescan.";
+        strings_["appx_import_interrupted"] = "The import was cut off, so the key may already be in the wallet. If its funds don't appear, run Settings → Rescan.";
+        strings_["appx_import_refused"] = "The node refused the request, so the key was not imported.";
+        strings_["stopconfirm_walletop_title"] = "A key import or rescan is running";
+        strings_["stopconfirm_walletop_body"] = "The node is scanning the chain for a key import or rescan. Stopping it now ends that scan early, and funds it has not reached yet appear only after Settings → Rescan.\n\nRecommended: close the wallet and leave the node running. It finishes the scan on its own.";
         strings_["reduce_motion"] = "Reduce Motion";
         strings_["tt_reduce_motion"] = "Disable animated transitions and balance lerp for accessibility";
         strings_["ago"] = "ago";