- Fix import sorting (I001) - Remove unused imports and variables (F401, F841) - Add noqa for test code (S106 hardcoded passwords, S314 XML parsing) - Auto-format with ruff format
- Add Model Mixins: TimestampMixin, SoftDeleteMixin, AuditMixin, etc. - Add Base Services: BaseService, BulkOperationsMixin, QueryOptimizerMixin - Add Base ViewSets with bulk operations - Add BackgroundJob model for Celery task tracking - Add BaseAppCommand for management commands - Add permissions, pagination, filters, cache, logging - Migrate tests to factory_boy + faker - Add CHANGELOG.md - 297 tests passing