fix(wallet): wait for the old node to fully exit before restarting on switch

After the stop, the switch started the replacement dragonxd too early — while the
old (direct-connected, unowned) node was still doing a slow graceful shutdown
(~70s; its network threads block on peer TLS timeouts) and holding the DATADIR
LOCK. The replacement couldn't acquire the lock, failed repeatedly, and the
crash-wedge left it stuck "starting". Root cause: the readiness poll used
isRpcPortInUse(), which on Windows is a connect() probe that reads "free" the
moment the daemon stops ACCEPTING RPC — early in shutdown, long before the
process exits and releases the datadir.

- EmbeddedDaemon::isDaemonProcessRunning(): true while any dragonxd process is
  alive (Windows findProcessByName; Linux /proc/<pid>/comm scan; macOS port
  fallback) — reflects the PROCESS, not just RPC acceptance.
- stopDaemonForWalletSwitch: for an UNOWNED node (no handle), after the RPC stop
  wait until BOTH the port is free AND isDaemonProcessRunning() is false, bounded
  ~120s (or ~5s if the stop couldn't be sent). Owned nodes are unchanged
  (stopEmbeddedDaemon() blocks for exit via the handle).
- Switch notification reworded to set the up-to-a-minute expectation (60s toast).

daemon_restarting_ stays set across the wait so the connect loop can't spawn a
competing daemon. Adversarially verified 6/6; fixes the seed-adopt path too.

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

src/app_network.cpp

@@ -1104,7 +1104,9 @@ void App::switchToWallet(const std::string& walletFile, bool stopDaemonConfirmed
     // can't surface (or sign outgoing chat) under the new wallet. It re-provisions from the new
     // wallet's seed once it connects. onDisconnected alone doesn't cover chat.
     resetChatSession();
-    ui::Notifications::instance().info("Switching wallet — the node will restart…");
+    ui::Notifications::instance().info(
+        "Switching wallet — stopping the node and restarting on the new wallet. "
+        "A graceful shutdown can take up to a minute.", 60.0f);
 
     async_tasks_.submit("Switch wallet", [this, needRescan](const util::AsyncTaskManager::Token&) {
         bool ok = false;