Strengthen deployment security and CI

[hiteshjakhar29]

Summary

• reinforce containerization and server hardening with a non-root multi-stage build, gunicorn tuning, and nginx security headers
• introduce validated environment configuration, request validation, caching, logging to PostgreSQL, and rate limiting for API endpoints
• add CI/CD workflow plus refreshed helper tooling and environment templates for dependable deployments

Testing

• pytest -q

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Codex Task