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/projects/list.html

@@ -101,7 +101,7 @@
                                 {% set plugin_colors = {
                                 'wordpress': 'bg-blue-500',
                                 'woocommerce': 'bg-purple-500',
-                                'wordpress_advanced': 'bg-indigo-500',
+                                'wordpress_specialist': 'bg-indigo-500',
                                 'gitea': 'bg-green-500',
                                 'n8n': 'bg-orange-500',
                                 'supabase': 'bg-emerald-500',
@@ -112,7 +112,7 @@
                                 {% set plugin_icons = {
                                 'wordpress': 'W',
                                 'woocommerce': 'WC',
-                                'wordpress_advanced': 'WA',
+                                'wordpress_specialist': 'WS',
                                 'gitea': 'G',
                                 'n8n': 'n8n',
                                 'supabase': 'SB',