[Epic] Move off Terraform Cloud

[samsimpson1]

User Need

As a Terraform maintainer
I want to move away from using Terraform Cloud for managing Terraform runs
so that I can save money and improve the developer experience

---

Context

(Add any extra context, links, diagrams, stakeholder interviews, etc.)

---

What’s Needed

List anything the solution must do or be (behaviour, performance, security, UX, etc.).

• Remove dependencies from Terraform Cloud-specific functionality or features
• Design a new way to run Terraform plans and applies on a different platform
• Migrate all Terraform workspaces to the new platform
• Update all documentation on how GOV.UK uses Terraform

---

Acceptance Criteria

Clear, measurable conditions to verify the story is complete and valuable.

• Terraform Cloud is no longer used for managing Terraform runs

---