Terraform Import & CI Setup

I already run a sizable AWS estate and now need the whole thing codified. The VPC stack—NAT Gateways, route tables, NACLs, endpoints, DHCP options sets, security groups, AWS Firewall rules—must be imported into Terraform, but that’s only part of the job. All existing EC2 instances, their attached EBS volumes and every S3 bucket in the account also have to be pulled into state while preserving their current, custom configurations.

The goal is a clean, reusable Terraform codebase stored in GitLab with a pipeline that automatically
• imports the existing resources into state without downtime
• performs `terraform plan` on merge requests
• gates `terraform apply` behind manual approval for production

I expect sensible module structure, remote state, and tags/variables that reflect our naming standards. Use native Terraform (1.5+), AWS CLI, and GitLab CI YAML; feel free to propose Terragrunt or tfenv if they simplify the workflow but keep the pipeline straightforward for my team to maintain.

Deliverable is the working repository plus a short hand-off guide that shows me how to run the pipeline, add new resources, and update state going forward.