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_tasks.py

@@ -0,0 +1,82 @@
+"""Tests for core Celery tasks"""
+
+
+from apps.core.tasks import (
+    BaseTask,
+    IdempotentTask,
+    PeriodicTask,
+    TimedTask,
+    TransactionalTask,
+)
+from celery import Task
+from django.test import TestCase
+
+
+class BaseTaskTest(TestCase):
+    """Tests for BaseTask"""
+
+    def test_inherits_from_celery_task(self):
+        """Test BaseTask inherits from Celery Task"""
+        self.assertTrue(issubclass(BaseTask, Task))
+
+    def test_has_default_retry_settings(self):
+        """Test BaseTask has default retry settings"""
+        self.assertEqual(BaseTask.max_retries, 3)
+        self.assertTrue(BaseTask.retry_backoff)
+        self.assertEqual(BaseTask.retry_backoff_max, 600)
+
+    def test_acks_late_enabled(self):
+        """Test acks_late is enabled"""
+        self.assertTrue(BaseTask.acks_late)
+
+    def test_reject_on_worker_lost(self):
+        """Test reject_on_worker_lost is enabled"""
+        self.assertTrue(BaseTask.reject_on_worker_lost)
+
+
+class TransactionalTaskTest(TestCase):
+    """Tests for TransactionalTask"""
+
+    def test_inherits_from_base_task(self):
+        """Test TransactionalTask inherits from BaseTask"""
+        self.assertTrue(issubclass(TransactionalTask, BaseTask))
+
+
+class IdempotentTaskTest(TestCase):
+    """Tests for IdempotentTask"""
+
+    def test_inherits_from_base_task(self):
+        """Test IdempotentTask inherits from BaseTask"""
+        self.assertTrue(issubclass(IdempotentTask, BaseTask))
+
+    def test_has_lock_timeout(self):
+        """Test IdempotentTask has lock_timeout attribute"""
+        self.assertEqual(IdempotentTask.lock_timeout, 3600)
+
+
+class TimedTaskTest(TestCase):
+    """Tests for TimedTask"""
+
+    def test_inherits_from_base_task(self):
+        """Test TimedTask inherits from BaseTask"""
+        self.assertTrue(issubclass(TimedTask, BaseTask))
+
+    def test_has_slow_threshold(self):
+        """Test TimedTask has slow_threshold attribute"""
+        self.assertEqual(TimedTask.slow_threshold, 60)
+
+
+class PeriodicTaskTest(TestCase):
+    """Tests for PeriodicTask"""
+
+    def test_inherits_from_timed_task(self):
+        """Test PeriodicTask inherits from TimedTask"""
+        self.assertTrue(issubclass(PeriodicTask, TimedTask))
+
+    def test_max_retries_is_one(self):
+        """Test max_retries is 1 for periodic tasks"""
+        self.assertEqual(PeriodicTask.max_retries, 1)
+
+    def test_autoretry_for_is_empty(self):
+        """Test autoretry_for is empty for periodic tasks"""
+        self.assertEqual(PeriodicTask.autoretry_for, ())