## CHANGES
- Add case-insensitive vendor lookup in VendorsManager
- Implement model name normalization in GetChatter method
- Add FilterByVendor method with case-insensitive matching
- Add FindModelNameCaseInsensitive helper for model queries
- Update group/item comparison to use case-insensitive checks
- Store vendors with lowercase keys internally
- Add comprehensive tests for case-insensitive functionality
- Fix vendor filtering for model listing command
## CHANGES
- Move domain types from common to domain package
- Move utility functions from common to util package
- Update all import statements across codebase
- Reorganize OAuth storage functionality into util package
- Move file management functions to domain package
- Update test files to use new package structure
- Maintain backward compatibility for existing functionality
