refactor(infra): remove decommissioned AWS terraform resources

[tasoo-oos]

Description

• 삭제 완료된 AWS failover 리소스 65개를 정리하고, 비게 된 infra/aws/decommission-stage 루트를 제거합니다.
• infra/aws/vpc, infra/aws/storage에 남아 있던 무효 removed 블록을 제거합니다.
• S3 게이트웨이 엔드포인트 경로를 보호하기 위해 private 라우트 테이블의 ignore_changes는 유지합니다.
• 삭제된 루트를 참조하던 legacy README를 갱신합니다.

Additional context

• 보안 그룹 5개가 상호 참조로 삭제 실패 → 죽은 참조 규칙 제거 후 재실행으로 완료.
• NAT 서버용 블랙홀 라우트는 별도로 제거하고, S3 엔드포인트 라우트는 유지했습니다.
• 사후 검증: 운영 클러스터 전 노드·워크로드 정상, 작업 중 재시작된 컨테이너 없음.
• 모든 변경사항은 이미 반영되었습니다.

PR리뷰해주시는 분들은 changed된 파일들 위주로 체크해주시면 감사하겠습니다.

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Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines
• Read the Contributing Guidelines and follow the Commit Convention
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

Closes TAS-2968

Summary by CodeRabbit

• Infrastructure Changes

  • Removed retired AWS resource configurations and import/state-transfer definitions from the decommissioning environment.
  • Removed management of legacy networking, load balancing, compute, IAM, messaging, observability, CDN, certificates, and database subnet resources.
  • Removed lifecycle protections and state-detachment declarations for resources no longer managed by these Terraform projects.
  • Updated private route-table documentation to reflect the retired NAT route while preserving the S3 endpoint route.

• Documentation

  • Simplified guidance for legacy Terraform projects and disabled failover infrastructure.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 12d550af-1131-4557-863e-a528d5bd17f3

📥 Commits

Reviewing files that changed from the base of the PR and between 5507cd0 and 544ae36.

📒 Files selected for processing (18)

• infra/aws/decommission-stage/.terraform.lock.hcl
• infra/aws/decommission-stage/README.md
• infra/aws/decommission-stage/cloudfront.tf
• infra/aws/decommission-stage/compute.tf
• infra/aws/decommission-stage/failover-network.tf
• infra/aws/decommission-stage/iam.tf
• infra/aws/decommission-stage/imports.tf
• infra/aws/decommission-stage/legacy-network.tf
• infra/aws/decommission-stage/load-balancing.tf
• infra/aws/decommission-stage/main.tf
• infra/aws/decommission-stage/message-queue.tf
• infra/aws/decommission-stage/observability.tf
• infra/aws/decommission-stage/removed.tf
• infra/aws/storage/removed.tf
• infra/aws/vpc/private-network.tf
• infra/aws/vpc/removed.tf
• infra/legacy/README.md
• infra/legacy/aws-failover/README.md

💤 Files with no reviewable changes (16)

• infra/aws/decommission-stage/compute.tf
• infra/aws/storage/removed.tf
• infra/aws/decommission-stage/removed.tf
• infra/aws/decommission-stage/.terraform.lock.hcl
• infra/legacy/aws-failover/README.md
• infra/aws/decommission-stage/main.tf
• infra/aws/decommission-stage/README.md
• infra/aws/decommission-stage/iam.tf
• infra/aws/decommission-stage/message-queue.tf
• infra/aws/decommission-stage/observability.tf
• infra/aws/decommission-stage/failover-network.tf
• infra/aws/decommission-stage/load-balancing.tf
• infra/aws/decommission-stage/cloudfront.tf
• infra/aws/decommission-stage/legacy-network.tf
• infra/aws/decommission-stage/imports.tf
• infra/aws/vpc/removed.tf

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The change removes the decommission-stage Terraform root, its staged AWS resources, and state-detachment blocks. It also updates the VPC route comment and retired infrastructure documentation.

Changes

Terraform decommission cleanup

Layer / File(s)	Summary
Remove decommission-stage root and state transfers infra/aws/decommission-stage/main.tf, infra/aws/decommission-stage/.terraform.lock.hcl, infra/aws/decommission-stage/imports.tf, infra/aws/decommission-stage/removed.tf	The provider configuration, lock file, import blocks, and state-detachment blocks are removed.
Remove staged AWS resources infra/aws/decommission-stage/cloudfront.tf, compute.tf, failover-network.tf, iam.tf, legacy-network.tf, load-balancing.tf, message-queue.tf, observability.tf	Staged networking, compute, IAM, load-balancing, messaging, observability, certificate, and CloudFront resources are removed.
Reconcile active Terraform state infra/aws/vpc/removed.tf, infra/aws/storage/removed.tf, infra/aws/vpc/private-network.tf	VPC and storage state-detachment blocks are removed. The private route table comment is updated.
Update retired infrastructure documentation infra/aws/decommission-stage/README.md, infra/legacy/README.md, infra/legacy/aws-failover/README.md	The decommission-stage documentation is deleted. Retired infrastructure workflow notes are updated or removed.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~30 minutes

Change: Refactor

Merge Risk: ⚪ Minimal · up to 544ae

The infrastructure cleanup is consistent with the documented decommissioning workflow and no merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	Issue #123 requires a frontend ProgressCard component for workbook progress. The component must support title, header, description, type, total, and complete. The reviewed changes only d…	Add the ProgressCard component with the required props and add automated tests for its rendering and progress data.
Out of Scope Changes check	⚠️ Warning	The changes delete the infra/aws/decommission-stage Terraform root, remove AWS failover resources and removed blocks, modify VPC route-table lifecycle configuration, and update legacy infrastructu…	Remove the unrelated AWS infrastructure and README changes from this pull request, or link them to the appropriate infrastructure issue and submit the #123 implementation separately.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: removing decommissioned AWS Terraform resources and related infrastructure configuration.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…

Full details: Linked Issues check

Explanation

Issue #123 requires a frontend ProgressCard component for workbook progress. The component must support title, header, description, type, total, and complete. The reviewed changes only delete AWS Terraform resources and update infrastructure README files. No ProgressCard implementation or automated test is present in the review evidence.

Full details: Out of Scope Changes check

Explanation

The changes delete the infra/aws/decommission-stage Terraform root, remove AWS failover resources and removed blocks, modify VPC route-table lifecycle configuration, and update legacy infrastructure README files. These changes have no demonstrated connection to issue #123, which concerns a frontend workbook progress card.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch t2968-remove-decommission-stage

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[sunghyun1000]

LGTM