- Create App\Traits\ResponseTrait that wraps CodeIgniter\API\ResponseTrait
- Add json_helper with convert_empty_strings_to_null() and prepare_json_response() functions
- Replace all imports of CodeIgniter\API\ResponseTrait with App\Traits\ResponseTrait across all controllers
- Add 'json' helper to BaseController helpers array
- Ensure consistent API response formatting across the application
- Rename all controllers from X.php to XController.php format
- Add new RefTxtModel for text-based reference ranges
- Rename group_dialog.php to grp_dialog.php and remove title_dialog.php
- Add comprehensive test suite for v2/master/TestDef module
- Update Routes.php to reflect controller renames
- Remove obsolete data files (clqms_v2.sql, lab.dbml)
