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>

res/lang/de.json

@@ -1294,6 +1294,13 @@
     "sweep_to": "Gefegt an:",
     "sweep_toggle": "In meine Wallet fegen (Schlüssel nicht behalten)",
     "sweep_tx": "Transaktion:",
+    "switch_progress_background": "Im Hintergrund fortsetzen",
+    "switch_progress_failed_title": "Wallet-Wechsel fehlgeschlagen",
+    "switch_progress_hint": "Ein sauberes Herunterfahren kann bis zu einer Minute dauern.",
+    "switch_progress_reconnecting": "Neu verbinden",
+    "switch_progress_starting": "Knoten wird mit der neuen Wallet gestartet",
+    "switch_progress_stopping": "Aktueller Knoten wird gestoppt",
+    "switch_progress_title": "Wallet wird gewechselt",
     "switch_stopnode_body": "Beim Wallet-Wechsel wird der Knoten mit der ausgewählten Wallet neu gestartet. Der laufende Knoten wird gestoppt und mit der neuen Wallet neu gestartet – wenn Sie ihn absichtlich laufen ließen, startet er automatisch wieder.",
     "switch_stopnode_confirm": "Knoten stoppen & wechseln",
     "switch_stopnode_title": "Laufenden Knoten stoppen?",