feat(settings): migrate Export All Keys modal to the reference design

Phase 1. DialogWarningHeader care header (was a hand-rolled red icon+text);
centered DialogActionFooter (Export + Close) replacing the StyledButtons + two
separators; on full success the saved path shows in a copy field with a green
check, partial/error render inline; export progress uses LoadingDots. Full i18n:
the previously-hardcoded notification + status strings now use TR (8 new
export_keys_* keys in en + 8 langs). Added hide() + a modal-export-all-keys sweep
surface. Also fixes a latent Begin/EndOverlayDialog imbalance on the 0-address
early return. No change to the export RPC logic.

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

src/app_sweep.cpp

@@ -20,6 +20,7 @@
 #include "ui/windows/send_tab.h"
 #include "ui/windows/wallets_dialog.h"
 #include "ui/windows/export_transactions_dialog.h"
+#include "ui/windows/export_all_keys_dialog.h"
 #include "ui/windows/daemon_download_dialog.h"
 #include "ui/windows/xmrig_download_dialog.h"
 #include "ui/pages/settings_page.h"
@@ -269,6 +270,8 @@ void App::buildSweepCatalog()
         [](App& a) { a.show_export_key_ = true; }, [](App& a) { a.show_export_key_ = false; });
     add("modal-export-transactions", ui::NavPage::Settings,
         [](App&) { ui::ExportTransactionsDialog::show(); }, [](App&) { ui::ExportTransactionsDialog::hide(); });
+    add("modal-export-all-keys", ui::NavPage::Settings,
+        [](App&) { ui::ExportAllKeysDialog::show(); }, [](App&) { ui::ExportAllKeysDialog::hide(); });
     add("modal-backup", ui::NavPage::Overview,
         [](App& a) { a.show_backup_ = true; }, [](App& a) { a.show_backup_ = false; a.backup_status_.clear(); });
     add("modal-about", ui::NavPage::Overview,