fix: Tier-2 UX robustness — action guards, in-progress guards, input trimming

The app-wide "import-key pattern" fixes (missing guards / untrimmed input / no
re-entrancy protection), from the robustness audit:

- Import-key dialog: unify the type indicator and the RPC dispatch on one
  classifier (classifyPrivateKey is now prefix-aware — an "SK..." shielded key no
  longer misroutes to the transparent RPC), trim manual input (not just Paste),
  and gate both the indicator and the Import button on a shared
  isRecognizedPrivateKey() so unrecognized/empty input can't be submitted.
- Shield: guard the submit button on connected + !syncing (like Send), with a
  disabled tooltip, instead of firing into a raw daemon error.
- Mining: disable the pool Mine button when the payout address is empty
  ("enter a payout address first"), and trim the pool URL/worker on persist.
- Console: track in-flight RPC commands (atomic counter + busy() override) so the
  input is disabled while a command runs instead of piling up on the worker.
- Maintenance (rescan/repair/delete-chain/reinstall-daemon): re-entrancy guard —
  bail with "already in progress" instead of launching a duplicate destructive op.
- Bootstrap dialog: re-attach to an in-flight download on reopen instead of
  resetting state and orphaning the running worker.

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

src/ui/windows/console_command_executor.cpp

@@ -54,6 +54,7 @@ void FullNodeConsoleExecutor::submit(const std::string& cmd)
 
     rpc::RPCWorker* worker = app_->consoleWorker();
     if (worker) {
+        in_flight_.fetch_add(1);   // gates busy() so the input is disabled until this returns
         worker->post([rpc, method, params, this]() -> rpc::RPCWorker::MainCb {
             std::string result_str;
             bool is_error = false;
@@ -65,6 +66,7 @@ void FullNodeConsoleExecutor::submit(const std::string& cmd)
                 is_error = true;
             }
             return [this, result_str, is_error]() {
+                in_flight_.fetch_sub(1);
                 std::lock_guard<std::mutex> lk(results_mutex_);
                 results_.push_back({result_str, is_error});
             };