feat(wallet): live progress modal for wallet switching

The "Stop the running node?" confirm modal now stays open through the entire
switch — stop → wait-for-exit → start → reconnect — showing a live phase, and
auto-closes the moment the new node connects. This turns the up-to-a-minute
graceful-shutdown wait from an apparent freeze into visible progress.

- WalletSwitchPhase (Stopping/Starting/Reconnecting/Failed) + atomic phase and
  dialog-open flags; the worker advances the phase, onConnected closes the modal,
  and a failed switch shows the accurate reason with a Close button.
- Owned switches (no confirm) also show the progress modal directly.
- "Continue in background" escape hatch so a long rescan / a hung startup never
  traps the user (the switch keeps running; a toast reports the result).
- isWalletSwitchInProgress() keeps the frame loop redrawing so the phase text and
  spinner animate while otherwise idle.
- i18n (EN + 8 languages, additive) + a modal-switch-progress sweep surface.

State machine adversarially verified 6/6 (thread-safety, no stuck modal,
confirm→progress transition, owned/unowned, no phase leak, redraw scoping).

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

src/util/i18n.cpp

@@ -1045,6 +1045,14 @@ void I18n::loadBuiltinEnglish()
         strings_["switch_stopnode_warn"] = "A node is already running that this wallet didn't start.";
         strings_["switch_stopnode_body"] = "Switching wallets restarts the node on the wallet you selected. The running node will be stopped and relaunched on the new wallet — if you kept it running on purpose, it comes back up automatically.";
         strings_["switch_stopnode_confirm"] = "Stop node & switch";
+        // Wallet-switch live progress modal
+        strings_["switch_progress_title"] = "Switching wallet";
+        strings_["switch_progress_failed_title"] = "Wallet switch failed";
+        strings_["switch_progress_stopping"] = "Stopping the current node";
+        strings_["switch_progress_starting"] = "Starting the node on the new wallet";
+        strings_["switch_progress_reconnecting"] = "Reconnecting";
+        strings_["switch_progress_hint"] = "A graceful shutdown can take up to a minute.";
+        strings_["switch_progress_background"] = "Continue in background";
 
         // Receive Tab
         strings_["receiving_addresses"] = "Your Receiving Addresses";