feat: rewrite entire project from Go to Rust

[kiro-agent]

This pull request was created by @kiro-agent on behalf of @toricls 👻

Comment with /kiro fix to address specific feedback or /kiro all to address everything.
_{Learn about Kiro autonomous agent}

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Summary

Complete rewrite of the acos CLI tool from Go to Rust, maintaining all existing functionality.

Changes

• Language: Go → Rust (2021 edition)
• CLI parsing: flag → clap (derive-based)
• Interactive prompts: survey/v2 → dialoguer
• Table output: tablewriter → comfy-table
• AWS SDK: aws-sdk-go-v2 → AWS SDK for Rust (aws-sdk-costexplorer, aws-sdk-organizations, aws-sdk-sts, aws-sdk-iam)
• Async runtime: tokio
• Error handling: anyhow
• JSON serialization: serde + serde_json

Functionality preserved

• List AWS accounts from Organizations (paginated)
• Filter by OU (--ou) or specific account IDs (--account-ids)
• Interactive multi-select account picker
• Fallback to STS GetCallerIdentity + IAM ListAccountAliases when Organizations is unavailable
• Cost Explorer integration (this month, last month, daily/weekly increase)
• Table and JSON output formats
• --as-of and --compared-to options

Project structure

src/
├── main.rs          # CLI entry point, table/JSON output, account selection
├── config.rs        # AWS SDK configuration loader
├── organization.rs  # Organizations API (list accounts, list by OU)
├── cost.rs          # Cost Explorer API (get costs, build filters)
└── sts.rs           # STS + IAM fallback for account info

Build & run

make build       # builds release binary to ./dist/acos
make run         # cargo run
make test        # cargo test
make fmt         # cargo fmt
make lint        # cargo clippy

Notes

• Compiles cleanly with zero clippy warnings
• CLI flags use kebab-case (--account-ids, --as-of, --compared-to) per Rust CLI conventions