docs: add pt-BR operational tutorial and README link

[chrystianmartins]

Motivation

• Provide an immediate, practical operational guide for a deployed environment (Coordinator + Gateway) so operators can bootstrap, manage via web (Swagger), run clients through the Gateway, and handle common troubleshooting and security recommendations.
• Make the tutorial discoverable from the repository README.md to help on-call engineers and deployers find operational instructions quickly.

Description

• Add docs/tutorial-operacao-ptbr.md containing a step-by-step operational tutorial in Portuguese covering service roles, Swagger/OpenAPI usage, user bootstrapping, API key creation, worker lifecycle (register/heartbeat), admin endpoints, consumption examples, observability, security recommendations, and troubleshooting.
• Update README.md to include a link to the new docs/tutorial-operacao-ptbr.md for easier discovery.
• This change is documentation-only and does not modify runtime code or application logic.

Testing

• Ran pytest pool-coordinator/tests/test_health.py pool-gateway/tests/test_health.py, which failed to execute in this environment due to a missing test dependency (httpx) required by starlette.testclient.
• Attempted curl -sS http://212.56.35.111:8001/health && curl -sS http://212.56.35.111:8002/health from the environment, but the connections were refused and could not be validated here.
• No automated tests were changed and documentation build/manual checks were limited to file creation and README update verification which succeeded locally.

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Codex Task