Restrict settings interface and material validation features based on user type:
- SettingsTab: User type only sees "Test ERP Connection" and "Test Database Connection" buttons; Admin sees full configuration interface
- MaterialValidationTab: Hide manager filter and data source options from non-admin users; default to database_filtered mode
- test_db_connection(): Read from config directly to support User type without UI variables
- Add backward compatibility: no session_manager defaults to full interface
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
