feat(v3.13.0): settings live DB reads, remove Directus/Appwrite, admin stats

Settings fixes:
- MAX_SITES_PER_USER, USER_RATE_LIMIT_PER_MIN/HR now read from DB settings
  table (DB > ENV > default), so dashboard/settings changes apply without
  restart. Sync cache refreshed on every save or delete.
- /api/me reports the live DB value for max_sites_per_user.

Admin improvements:
- Admin users bypass per-user rate limiting entirely (role=admin or ADMIN_EMAILS).
- Admin Overview now shows platform stats: registered users, new users (7d),
  total user sites, available tools.

Plugin cleanup:
- Appwrite and Directus plugins removed from the active registry (8 plugins
  now: WordPress, WooCommerce, WordPress Specialist, Gitea, n8n, Supabase,
  OpenPanel, Coolify). Plugin code is retained for future re-enabling.
- Settings page plugin visibility list updated to match.

Mobile onboarding:
- Stepper steps on narrow viewports stack vertically with correct full border
  and rounded corners on each step.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/templates/dashboard/login.html

@@ -93,7 +93,7 @@
             {% endif %}
 
             <!-- Login Form -->
-            <form method="POST" action="/dashboard/login" class="space-y-6">
+            <form method="POST" action="/dashboard-legacy/login" class="space-y-6">
                 <input type="hidden" name="csrf_token" value="{{ request.state.csrf_token }}">
                 <input type="hidden" name="next" value="{{ next_url }}">
 
@@ -160,4 +160,4 @@
     </div>
 </body>
 
-</html>
+</html>