Add usage examples

We need practical examples showing how to use this project in real-world environments.

Suggested examples:

* Local development using `.env`
* GitHub Actions validation step without `.env`
* Kubernetes deployment
* HashiCorp Nomad job

The goal is to create an `examples/` directory with one folder per environment.

Suggested structure:

```txt
examples/
├── local-env/
├── github-actions/
├── kubernetes/
└── hashicorp-nomad/
```

Each example should include a small `README.md` explaining:

* What the example does
* How to run it
* Which environment variables are required
* Expected success and failure behavior

Important: `.env` files should only be used for local development. CI/CD and production examples should use environment variables, secrets, or secret managers instead.

> Contributors can start by adding just one example.

Start by reviewing the repository structure and the issue's proposed examples/ layout. Add one environment folder, such as local-env, github-actions, or kubernetes, with a README.md covering its purpose, usage, required environment variables, and expected success and failure behavior. Keep .env usage limited to local development and document secret-based configuration for CI/CD or production.

Written by the indexing model from the issue text.