Get started: Supported cloud providers

[pavithraes]

Goal

Cloud provider overview — at-a-glance table: AWS ✅ full, Hetzner ✅ full (recommended starter), GCP / Azure / Local 🚧 planned. Short "why Hetzner first?" callout.

Acceptance criteria

• Provider support matrix is added to /docs/get-started/providers - (generalized because we also have local, but open to suggestions) - Also, if this is a short list, maybe fold it into the landing page /docs/get-started/
• Provider support matrix is accurate and links to each provider's how-to

References

• https://github.com/nebari-dev/nebari-infrastructure-core/blob/main/docs/cli-reference.md#configuration