- Update IS_STORAGE_CONFIGURED to only require S3_REGION and S3_BUCKET_NAME
- Make S3_ACCESS_KEY and S3_SECRET_KEY optional in S3 client creation
- Allow AWS SDK to use IAM roles, instance profiles, and credential chains
- Maintain backward compatibility with explicit credentials and MinIO
- Update tests to reflect new IAM role authentication behavior
BREAKING CHANGE: IS_STORAGE_CONFIGURED now returns true with only region and bucket configured