chore: remove admin SPA and update to two-app production setup

Remove apps/admin/ entirely — platform admin functionality now lives
in apps/app/ under /platform/* routes for super_admin users.

Production URL scheme changed:
- Organizer app: crewli.app (was app.crewli.app)
- Portal: portal.crewli.app (unchanged)
- API: api.crewli.app (unchanged)
- admin.crewli.app and app.crewli.app retired

Backend:
- Removed FRONTEND_ADMIN_URL config and admin cookie (crewli_admin_token)
  from SetAuthCookie, CookieBearerToken, cors.php, app.php
- Updated .env and .env.example (two origins, no port 5173)
- Updated cookie test: admin origin test → unknown origin fallback test

Infrastructure:
- Makefile: removed admin target
- deploy/nginx: updated CSP comment, removed admin vhost
- Updated README.md, CLAUDE.md, and all dev-docs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.cursor/rules/001_workspace.mdc

@@ -6,7 +6,7 @@ alwaysApply: true
 
 # Workspace Rules
 
-You are an expert full-stack developer working on Crewli, a multi-tenant SaaS platform for event and festival management. The backend is a Laravel 12 REST API (JSON only, no Blade), and three Vue 3 SPA frontends communicate via CORS + Sanctum tokens.
+You are an expert full-stack developer working on Crewli, a multi-tenant SaaS platform for event and festival management. The backend is a Laravel 12 REST API (JSON only, no Blade), and two Vue 3 SPA frontends communicate via CORS + Sanctum tokens.
 
 ## Tech Stack
 
@@ -56,7 +56,7 @@ crewli/
 │   └── tests/Feature/Api/V1/
 │
 ├── apps/
-│   ├── admin/                   # Super Admin SPA (Vuexy full)
+│   ├── app/                     # Organizer + Platform Admin SPA (Vuexy full) - MAIN APP
 │   │   └── src/
 │   │       ├── @core/           # Vuexy core (NEVER modify)
 │   │       ├── @layouts/        # Vuexy layouts (NEVER modify)
@@ -68,9 +68,6 @@ crewli/
 │   │       ├── stores/          # Pinia stores
 │   │       └── types/           # TypeScript interfaces
 │   │
-│   ├── app/                     # Organizer SPA (Vuexy full) - MAIN APP
-│   │   └── src/                 # Same structure as admin/
-│   │
 │   └── portal/                  # External Portal SPA (Vuexy stripped)
 │       └── src/                 # No sidebar, no customizer, top-bar only
 │