- Introduced `ImageSnapshotResponse` dataclass for image snapshot API
- Migrated `scan_service` state to use `ScanStatus` dataclass
- Replaced dictionary subscripting with attribute access in `api.py`
- Added type annotations to `check_api_dataclass_usage.py` to satisfy CI
- Fixed `get_scan_status` to return serialized dataclass
This resolves "Forbidden subscript access" errors reported by CI.