feat(wallet): wallet-files list + switching (P2)

Second phase of multi-wallet: list wallet files and switch the active one.

- Daemon plumbing: EmbeddedDaemon::setWalletFile -> start() passes -wallet=<name>
  (non-default only; skipped during the isolated seed-migration start), and
  DaemonController::syncSettings pushes active_wallet_file on each start.
- App::switchToWallet: persist the new active wallet, then stop + restart the
  node on -wallet=<name> (rescan only if it was never synced in this datadir).
  Reuses the seed-adopt restart coordination; WalletState clears on disconnect
  and the P1 identity-scoped caches re-key, so no previous-wallet data leaks.
  Guarded: full-node, embedded daemon, not mid-restart, no pending send.
- Wallets dialog (Settings -> Backup & Data -> "Wallets…"): a table of wallet
  files (datadir wallet*.dat + user-added folders' *.dat) with size (disk) and
  cached balance / address count / last-opened (wallet index), a current/Active
  badge, Open (switch), and Add folder. Out-of-datadir wallets show "import to
  open" (P3). Added as a sweep surface.
- Mining payout safety: non-destructive warning if the pool-mode worker looks
  like a DragonX address not in the current wallet (stale after a switch).

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

src/daemon/embedded_daemon.cpp

@@ -488,6 +488,14 @@ bool EmbeddedDaemon::start(const std::string& binary_path)
         args.push_back("-maxconnections=" + std::to_string(max_connections_));
     }
 
+    // Active wallet file (multi-wallet). The daemon loads <datadir>/<name>. Only pass it for a
+    // non-default name so the common case's command line is unchanged; skip during an isolated
+    // start (seed migration manages its own throwaway wallet).
+    if (!wallet_file_.empty() && wallet_file_ != "wallet.dat" && override_datadir_.empty()) {
+        DEBUG_LOGF("[INFO] Loading wallet file: %s\n", wallet_file_.c_str());
+        args.push_back("-wallet=" + wallet_file_);
+    }
+
     // Add wallet-repair flag if requested (one-shot). -zapwallettxes=2 wipes all wallet tx/note
     // records and rebuilds them from the chain; it implies -rescan, so don't also pass -rescan.
     if (zap_on_next_start_.exchange(false)) {