security(console): mask key-dump command RESULTS in the scrollback

The console redacted secret command ARGS but showed the OUTPUT of key-revealing
commands (dumpprivkey / z_exportkey / z_exportviewingkey / z_exportmnemonic /
dumpwallet / z_exportwallet, and the lite seed/export verbs) in full — visible
in the scrollback, Copy All, Ctrl+C and the filter. Now, when the submitted
command is key-revealing, its result is held ONLY in a member buffer (never in
the scrollback model, so Copy-All etc. can't leak it) and a masked placeholder
is shown. An explicit "Copy secret" button routes through the auto-clearing
clipboard; the buffer auto-wipes after 60s, on Clear, and on wallet lock
(via wipeDisplayedSecrets). The command string passed to the executor is
byte-identical. New pure helper ConsoleCommandRevealsSecret is unit-testable.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app.cpp

@@ -162,6 +162,7 @@ void App::wipeDisplayedSecrets()
     show_seed_backup_ = false;
     sodium_memzero(export_result_, sizeof(export_result_));
     ui::KeyExportDialog::hide();   // zeros its static s_key via secureWipeLiteSecret
+    console_tab_.wipeSecretResult();   // drop any masked key-dump result held in the console
 }
 
 // Enqueue a blocking xmrig start/stop op onto the dedicated serialized control thread so the render thread
@@ -2411,6 +2412,8 @@ void App::render()
                     console_exec_ = std::make_unique<ui::LiteConsoleExecutor>(this);
                 else
                     console_exec_ = std::make_unique<ui::FullNodeConsoleExecutor>(this);
+                // One-time: route the console's "Copy secret" through the auto-clearing clipboard.
+                console_tab_.setCopySecretHandler([this](const std::string& s) { copySecretToClipboard(s); });
             }
             console_tab_.render(*console_exec_);
             // Persist the console toolbar toggles (ConsoleTab has no settings pointer). Save only when