Add usage examples

[fontebasso]

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:

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.