feat(phase-21): add V3 demo seed, DataSource and DetectionRule models (T-200, T-201, T-202)

backend/app/models/__init__.py

@@ -7,10 +7,13 @@ from app.models.evidence import Evidence
 from app.models.intel import IntelItem
 from app.models.audit import AuditLog
 from app.models.notification import Notification
+from app.models.data_source import DataSource
+from app.models.detection_rule import DetectionRule
 from app.models.enums import TechniqueStatus, TestState, TestResult, TeamSide
 
 __all__ = [
     "User", "Technique", "Test", "TestTemplate", "Evidence",
-    "IntelItem", "AuditLog", "Notification",
+    "IntelItem", "AuditLog", "Notification", "DataSource",
+    "DetectionRule",
     "TechniqueStatus", "TestState", "TestResult", "TeamSide",
 ]