feat: enhance article import functionality with reference management

feat: implement row level security and supplier status management

Add article import functionality with CSV and Excel support, including API endpoints for starting imports, listing imports, and handling import errors. Implement background processing for imports, validation, and error handling. Update requirements and documentation accordingly.

Add FastAPI application structure with Prisma integration, including API endpoints, services, repositories, and database setup. Introduce strict layering rules, documentation, and testing strategy.