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/plugin_visibility.py

@@ -7,15 +7,24 @@ plugins listed in the ENABLED_PLUGINS setting (DB > ENV > default).
 Usage:
     from core.plugin_visibility import get_public_plugin_types, is_plugin_public
 
-    public_types = get_public_plugin_types()  # {"wordpress", "woocommerce", "supabase"}
+    public_types = get_public_plugin_types()
     if is_plugin_public("gitea"):  # True
         ...
 """
 
 import os
 
-# Default plugins available to public (OAuth) users
-DEFAULT_PUBLIC_PLUGINS = {"wordpress", "woocommerce", "supabase", "openpanel", "gitea"}
+# Default plugins available to public (OAuth) users.
+DEFAULT_PUBLIC_PLUGINS = {
+    "wordpress",
+    "woocommerce",
+    "wordpress_specialist",
+    "supabase",
+    "openpanel",
+    "gitea",
+    "n8n",
+    "coolify",
+}
 
 
 def _parse_plugins(val: str) -> set[str]: