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/keys/list.html

@@ -275,10 +275,8 @@
             <p class="text-sm text-green-700 dark:text-green-400">
                 {% if lang == 'fa' %}
                 <strong>نکته:</strong> فقط آدرس URL کافی است. هنگام اتصال می‌توانید با <strong>API Key</strong> یا <strong>GitHub/Google</strong> احراز هویت کنید.
-                ساخت <a href="/dashboard/oauth-clients{% if lang and lang != 'en' %}?lang={{ lang }}{% endif %}" class="underline">OAuth Client</a> اختیاری است.
                 {% else %}
                 <strong>Tip:</strong> You only need the URL above. When connecting, you can authenticate with an <strong>API Key</strong> or <strong>GitHub/Google</strong>.
-                Creating an <a href="/dashboard/oauth-clients{% if lang and lang != 'en' %}?lang={{ lang }}{% endif %}" class="underline">OAuth Client</a> is optional.
                 {% endif %}
             </p>
         </div>