feat(core): add core module with mixins, services, and background jobs

- 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

tests/apps/core/test_mixins.py

@@ -0,0 +1,110 @@
+"""Тесты для Model Mixins."""
+
+from apps.core.mixins import (
+    OrderableMixin,
+    SoftDeleteMixin,
+    StatusMixin,
+)
+from django.test import TestCase
+
+
+class TimestampMixinTest(TestCase):
+    """Тесты для TimestampMixin."""
+
+    def test_created_at_auto_set(self):
+        """Проверка автоматической установки created_at."""
+        # Используем BackgroundJob как пример модели с TimestampMixin
+        from apps.core.models import BackgroundJob
+
+        job = BackgroundJob.objects.create(
+            task_id="test-task-1",
+            task_name="test.task",
+        )
+        self.assertIsNotNone(job.created_at)
+        self.assertIsNotNone(job.updated_at)
+
+    def test_updated_at_auto_update(self):
+        """Проверка автоматического обновления updated_at."""
+        from apps.core.models import BackgroundJob
+
+        job = BackgroundJob.objects.create(
+            task_id="test-task-2",
+            task_name="test.task",
+        )
+        original_updated = job.updated_at
+
+        # Обновляем запись
+        job.progress = 50
+        job.save()
+        job.refresh_from_db()
+
+        self.assertGreaterEqual(job.updated_at, original_updated)
+
+
+class UUIDPrimaryKeyMixinTest(TestCase):
+    """Тесты для UUIDPrimaryKeyMixin."""
+
+    def test_uuid_auto_generated(self):
+        """Проверка автоматической генерации UUID."""
+        from apps.core.models import BackgroundJob
+
+        job = BackgroundJob.objects.create(
+            task_id="test-task-3",
+            task_name="test.task",
+        )
+        self.assertIsNotNone(job.id)
+        # Проверяем что ID похож на UUID (строка 32+ символа с дефисами)
+        self.assertEqual(len(str(job.id)), 36)
+
+    def test_uuid_unique(self):
+        """Проверка уникальности UUID."""
+        from apps.core.models import BackgroundJob
+
+        job1 = BackgroundJob.objects.create(
+            task_id="test-task-4a",
+            task_name="test.task",
+        )
+        job2 = BackgroundJob.objects.create(
+            task_id="test-task-4b",
+            task_name="test.task",
+        )
+        self.assertNotEqual(job1.id, job2.id)
+
+
+class SoftDeleteMixinTest(TestCase):
+    """Тесты для SoftDeleteMixin."""
+
+    def test_soft_delete_mixin_fields(self):
+        """Проверка наличия полей is_deleted и deleted_at."""
+        # Проверяем что поля определены в миксине
+        field_names = [f.name for f in SoftDeleteMixin._meta.get_fields()]
+        self.assertIn("is_deleted", field_names)
+        self.assertIn("deleted_at", field_names)
+
+    def test_soft_delete_queryset_methods(self):
+        """Проверка методов SoftDeleteQuerySet."""
+        from apps.core.mixins import SoftDeleteQuerySet
+
+        # Проверяем что методы определены
+        self.assertTrue(hasattr(SoftDeleteQuerySet, "alive"))
+        self.assertTrue(hasattr(SoftDeleteQuerySet, "dead"))
+        self.assertTrue(hasattr(SoftDeleteQuerySet, "hard_delete"))
+
+
+class StatusMixinTest(TestCase):
+    """Тесты для StatusMixin."""
+
+    def test_status_choices(self):
+        """Проверка наличия статусов."""
+        self.assertEqual(StatusMixin.Status.DRAFT, "draft")
+        self.assertEqual(StatusMixin.Status.ACTIVE, "active")
+        self.assertEqual(StatusMixin.Status.INACTIVE, "inactive")
+        self.assertEqual(StatusMixin.Status.ARCHIVED, "archived")
+
+
+class OrderableMixinTest(TestCase):
+    """Тесты для OrderableMixin."""
+
+    def test_orderable_mixin_has_order_field(self):
+        """Проверка наличия поля order."""
+        self.assertTrue(hasattr(OrderableMixin, "order"))