Add deployment architecture documentation

Author: codicecustode

docs/deployment.md

@@ -0,0 +1,29 @@
+## Deployment Architecture
+
+Application is deployed on an Azure Virtual Machine using Docker.
+
+Two environments are maintained on the same VM:
+
+- Staging → Container running on port 8001 (develop branch)
+- Production → Container running on port 8000 (main branch)
+
+Nginx reverse proxy routes traffic to appropriate containers.
+
+### Environment Variable Management
+
+Sensitive values are not stored in the repository.
+
+They are managed using:
+
+- GitHub Secrets for CI/CD authentication
+- Environment variables inside Docker runtime
+- Azure Key Vault can be used in real production
+
+### Rollback Strategy
+
+If deployment fails:
+
+- Previous commit can be reverted
+- Older Docker image can be redeployed
+- Container can be restarted with previous tag
+- GitHub Actions workflow can be re-run