Add LocalStack migration/adaptation plan and README pointer

[ongeziwe17]

Motivation

• Provide a clear, practical plan to add a LocalStack deployment mode so Terraform IaC can be validated locally without touching real AWS.
• Preserve the existing real-AWS deployment path while documenting how to run, test, and CI-validate a LocalStack mode.
• Capture repo inventory, resource suitability for LocalStack, recommended dual-mode layout, provider/backend patterns, variable gating, Docker Compose, developer workflow, CI guidance, and an implementation checklist.

Description

• Added docs/localstack-migration-plan.md, a comprehensive migration/adaptation plan (inventory, feasibility, dual-mode architecture, provider/backend examples, variable patterns, docker-compose proposal, Makefile snippets, CI recommendations, pros/cons, risk checklist, and step-by-step implementation order).
• Updated README.md with a new "LocalStack Deployment" section that points to the detailed plan and warns about LocalStack limitations (EC2/user-data/EIP/security-group differences).
• Plan includes example provider.localstack.tf, localstack.tfvars, docker-compose.localstack.yml proposal, conditional Terraform patterns (count / ami_id override), and CI workflow draft for LocalStack validation.
• Changes are additive and documentation-only; no existing Terraform resource code was removed or altered.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep mock AWS env vars for the whole recipe

In this proposed Makefile recipe, the inline AWS_* assignments only apply to the tflocal ... init command immediately following them; the && tflocal ... plan command runs as a separate simple command without those mock credentials/endpoints unless the user already exported them. When a developer copies this Makefile and runs make local-plan-backend from a clean shell, the plan step can therefore fall back to whatever ambient AWS configuration exists or fail credential checks, undermining the safety goal of these commands. Export the variables for the recipe/shell or repeat them on each command.

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