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/endpoints/__init__.py

@@ -7,7 +7,7 @@ Each endpoint exposes only the tools relevant to its purpose.
 Endpoints:
     /mcp              - Admin endpoint (all tools, requires Master API Key)
     /mcp/wordpress    - WordPress tools only (92 tools)
-    /mcp/wordpress-advanced - WordPress Advanced tools (22 tools)
+    /mcp/wordpress-specialist - WordPress Specialist tools (companion-backed)
     /mcp/gitea        - Gitea tools only (55 tools)
     /mcp/project/{id} - Project-specific tools