add initial version of prowler extension

[HarshCasper]

Summary

• Build a full LocalStack extension for Prowler with a Python backend and React frontend, served directly at /_extension/prowler
• Add scan orchestration that runs Prowler in a Docker sidecar, tracks scan lifecycle (idle/running/completed/failed), and exposes status/results through REST APIs
• Normalize and surface Prowler findings in a UI with severity summaries, filtering, search, sorting, and expandable finding details
• Integrate LocalStack-aware behavior across backend and frontend, including endpoint handling, service mapping, and extension path-safe API routing
• Add test coverage for extension health, scan request validation, concurrency behavior, and end-to-end insecure S3 detection workflow

Screenshot