feat(docker): add Docker deployment configuration

Add production-ready Docker setup with multi-stage Dockerfile, docker-compose
orchestration for API, PostgreSQL, Redis, and Nginx services. Includes
health checks, non-root user execution, and proper networking.

- Add multi-stage Dockerfile with gunicorn/gevent workers
- Add docker-compose.yml with api, db, redis, nginx services
- Add nginx reverse proxy configuration with security headers
- Update .env.example with Docker and production variables
- Add email provider configuration (Mailgun, SendGrid)
- Add requests dependency for HTTP client support
- Update documentation with Docker deployment guide
- Rebrand project name from Gatehouse to Secuird

config/base.py

@@ -123,7 +123,7 @@ class BaseConfig:
 
     # WebAuthn Configuration
     WEBAUTHN_RP_ID = os.getenv("WEBAUTHN_RP_ID", "localhost")
-    WEBAUTHN_RP_NAME = os.getenv("WEBAUTHN_RP_NAME", "Gatehouse")
+    WEBAUTHN_RP_NAME = os.getenv("WEBAUTHN_RP_NAME", "Secuird")
     WEBAUTHN_ORIGIN = os.getenv("WEBAUTHN_ORIGIN", "https://ui.webauthn.local")
 
     # Frontend URL (for OAuth callback redirects)
@@ -140,3 +140,15 @@ class BaseConfig:
     SMTP_USERNAME = os.getenv("SMTP_USERNAME", "")
     SMTP_PASSWORD = os.getenv("SMTP_PASSWORD", "")
     FROM_ADDRESS = os.getenv("FROM_ADDRESS", "noreply@gatehouse.local")
+
+    # Email Provider Configuration
+    EMAIL_PROVIDER = os.getenv("EMAIL_PROVIDER", "smtp").lower()  # smtp, mailgun, sendgrid
+    
+    # Mailgun Configuration (used when EMAIL_PROVIDER=mailgun)
+    MAILGUN_API_KEY = os.getenv("MAILGUN_API_KEY", "")
+    MAILGUN_DOMAIN = os.getenv("MAILGUN_DOMAIN", "")
+    MAILGUN_API_URL = os.getenv("MAILGUN_API_URL", "https://api.mailgun.net/v3")
+    
+    # SendGrid Configuration (used when EMAIL_PROVIDER=sendgrid)
+    SENDGRID_API_KEY = os.getenv("SENDGRID_API_KEY", "")
+    SENDGRID_FROM_EMAIL = os.getenv("SENDGRID_FROM_EMAIL", "")