Add first-run setup wizard

Full-screen onboarding at admin.php?page=aurora-admin-setup: Welcome →
Appearance (theme + font) → Branding (logo/favicon/rename) → Features
(replacement-screen toggles) → Done. Reuses SettingsField for every control
and applyLiveTheme for instant preview; finish/skip saves via wp/v2/settings
and marks completion.

- admin/src/Pages/SetupWizard.php: hidden submenu page, disables the shell on
  its own page (aurora_admin_shell_enabled filter) + hides native chrome,
  register_activation_hook sets a one-time redirect flag, admin_init redirects
  once, and a POST /aurora-admin/v1/setup/complete route marks it done.
- app/src/pages/setup-wizard/SetupWizard.vue + entries/setup-wizard.js + vite
  input.
- Wired into aurora-admin.php + AuroraAdmin.php.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

admin/src/App/AuroraAdmin.php

@@ -13,6 +13,7 @@ use AuroraAdmin\Options\Settings;
 use AuroraAdmin\Shell\Shell;
 use AuroraAdmin\Pages\DashboardTakeover;
 use AuroraAdmin\Pages\SettingsPage;
+use AuroraAdmin\Pages\SetupWizard;
 use AuroraAdmin\Rest\DashboardData;
 use AuroraAdmin\Analytics\Analytics;
 use AuroraAdmin\Rest\AnalyticsData;
@@ -63,6 +64,7 @@ class AuroraAdmin
     new Shell();
     new DashboardTakeover();
     new SettingsPage();
+    new SetupWizard();
     new DashboardData();
     new Analytics();
     new AnalyticsData();