feat(rules): add stopped RDS instance rule

[axonstone]

Summary

• Add a discovery-only RDS rule that flags DB instances in the stopped state for cleanup review.
• Add a discovery-only EC2 rule that flags reserved instances whose endTime fell within the last 30 days for renewal follow-up review.
• Register both rules in the AWS packs, document their public rule IDs, and add evaluator, export, metadata, and changeset coverage for @cloudburn/rules.

Diagram

flowchart LR
  subgraph Datasets["Discovery datasets"]
    RDS["aws-rds-instances"]
    RI["aws-ec2-reserved-instances"]
  end

  subgraph Rules["New rules"]
    RDSRule["CLDBRN-AWS-RDS-9\nStopped RDS DB instance"]
    RIRule["CLDBRN-AWS-EC2-12\nRecently expired EC2 reserved instance"]
  end

  subgraph Outputs["Review outcomes"]
    Cleanup["Cleanup review findings"]
    Renewal["Renewal follow-up findings"]
  end

  RDS --> RDSRule --> Cleanup
  RI --> RIRule --> Renewal

Loading

Scope

• cloudburn (cli)
• @cloudburn/sdk
• @cloudburn/rules
• docs/community files

Release Notes

• Added a .changeset/*.md file for published package changes
• No published package changes in this PR

Verification

• pnpm lint
• pnpm typecheck
• pnpm test
• pnpm build
• pnpm verify

Boundary Checks

• No engine/parser/provider logic added to @cloudburn/rules
• CLI delegates scan logic to SDK
• README/CONTRIBUTING/docs updated when behavior changed

Related Issues

• None found via gh issue list.

---

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.