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

src/apps/core/urls.py

@@ -0,0 +1,14 @@
+"""
+URL configuration for core app.
+"""
+
+from apps.core.views import HealthCheckView, LivenessView, ReadinessView
+from django.urls import path
+
+app_name = "core"
+
+urlpatterns = [
+    path("", HealthCheckView.as_view(), name="health"),
+    path("live/", LivenessView.as_view(), name="liveness"),
+    path("ready/", ReadinessView.as_view(), name="readiness"),
+]