- Create exceptions module (codes 9000-9005) following OCI provider pattern
- Replace all sys.exit(1) calls with typed exceptions
- Fix mutable default arguments in ImageProvider and CheckReportImage
- Add return type hints to all properties and methods
- Add ResourceGroup field to metadata dict
- Add test suite with 23 test cases covering initialization, finding
processing, scan execution, error handling, and connection testing
- Update CHANGELOG with container image provider entry