feat: add Campaign/Compliance domain entities and extract users/audit/data_sources to services (LP-2 through LP-6)

backend/app/domain/entities/__init__.py

@@ -1,3 +1,15 @@
+from app.domain.entities.campaign import CampaignEntity
+from app.domain.entities.compliance import (
+    ComplianceControlEntity,
+    ComplianceFrameworkEntity,
+    ControlCoverageStatus,
+)
 from app.domain.entities.technique import TechniqueEntity
 
-__all__ = ["TechniqueEntity"]
+__all__ = [
+    "CampaignEntity",
+    "ComplianceControlEntity",
+    "ComplianceFrameworkEntity",
+    "ControlCoverageStatus",
+    "TechniqueEntity",
+]