feat: Add staging environment for local production testing

- Add docker-compose.staging.yml with PostgreSQL and Django
- Add .env.staging.example with staging-specific environment variables
- Configure staging settings (DEBUG=False, no SSL redirect for localhost)
- Update settings/__init__.py to support staging environment detection
- Update AGENTS.md with staging environment documentation
- Update .gitignore to exclude .env.staging
- Optimize docker-compose.prod.yml configuration

Staging environment simulates production configuration locally:
- PostgreSQL database (port 5433 to avoid conflicts)
- Gunicorn with 4 workers
- DEBUG=False but HTTP allowed for easier testing
- Separate volumes for static files, media, and logs

Usage:
  cp .env.staging.example .env.staging
  docker compose -f docker-compose.staging.yml up -d

.env.staging.example

@@ -0,0 +1,51 @@
+# Staging Environment Variables
+# Testing de producción en localhost sin SSL
+# Este ambiente simula producción pero permite HTTP en localhost
+
+# Django Environment
+DJANGO_ENV=staging
+
+# Debug mode (False para simular producción)
+DEBUG=False
+
+# Django Secret Key
+# Para staging local, puedes usar una key fija (NO usar en producción real)
+SECRET_KEY=staging-local-key-zh6rinl@8y7g(cf781snisx2j%p^c#d&b2@@9cqe!v@4yv8x=v
+
+# Allowed hosts (localhost para testing)
+ALLOWED_HOSTS=localhost,127.0.0.1,0.0.0.0
+
+# CORS allowed origins (permite acceso desde navegador local)
+# Incluye común puertos de desarrollo de frontend y acceso directo
+CORS_ALLOWED_ORIGINS=http://localhost:8000,http://localhost:3000,http://localhost:5173,http://localhost:7001,http://127.0.0.1:8000
+
+# CSRF Trusted Origins (localhost HTTP para staging)
+CSRF_TRUSTED_ORIGINS=http://localhost:8000,http://127.0.0.1:8000
+
+# PostgreSQL Database Configuration (staging local)
+DB_NAME=tienda_ilusion_staging
+DB_USER=tienda_ilusion_user
+DB_PASSWORD=staging_local_password
+DB_HOST=postgres
+DB_PORT=5432
+
+# Email Configuration (console backend para staging)
+EMAIL_HOST=smtp.gmail.com
+EMAIL_PORT=587
+EMAIL_USE_TLS=True
+EMAIL_HOST_USER=staging@tiendailusion.local
+EMAIL_HOST_PASSWORD=staging_password
+DEFAULT_FROM_EMAIL=staging@tiendailusion.local
+
+# Admin notifications
+ADMIN_EMAIL=admin@tiendailusion.local
+
+# Tryton ERP Configuration (Staging)
+# Ajusta estos valores según tu entorno de staging de Tryton
+TRYTON_HOST=localhost
+TRYTON_DATABASE=tryton_staging
+TRYTON_USERNAME=admin
+TRYTON_PASSWORD=admin
+
+# Staging specific: Disable SSL redirect for localhost testing
+STAGING_DISABLE_SSL=True