fix: spoke README terraform-docs and tfvars gitignore

[JG-Cloud]

Summary

Two fixes required for Terraform Registry publication compliance:

• modules/spoke/README.md — populate the empty <!-- BEGIN_TF_DOCS --> block by running terraform-docs. The Registry parses this block to display submodule inputs/outputs; an empty block left a blank table on the Registry page for //modules/spoke.
• .gitignore — add *.tfvars / !*.tfvars.example to prevent accidental commits of real variable files containing account IDs or role ARNs.

Test plan

• CI pipeline passes (format, lint, validate, security, docs)
• modules/spoke/README.md contains populated Inputs and Outputs tables
• *.tfvars is blocked by .gitignore; *.tfvars.example files are still tracked

[github-actions]

Pull Request Review Status

• 🖌 Terraform Format and Style: success
• 🔍 Terraform Linting: success
• 👮 Terraform Security Check: success
• 👮 Terraform Security Checkov: success
• 🔘 Terraform Tests: success
• 🔧 Terraform Initialisation: success
• 🤖 Terraform Validation: success
• 🤖 Terraform Example Validation: failure
• 📖 Terraform Documentation: failure
• 🔖 Commitlint: success

Working Directory: .
Pusher: @JG-Cloud, Action: pull_request
Workflow Run Link: https://github.com/appvia/terraform-aws-devops-agent/actions/runs/26276349876