feat: SAC 0.7.0 display_name columns and event severity overrides

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/models/__init__.py

@@ -5,6 +5,7 @@ from app.models.notification_channel import NotificationChannel
 from app.models.notification_cooldown import NotificationCooldown
 from app.models.notification_policy import NotificationPolicy
 from app.models.problem import Problem, ProblemEvent
+from app.models.event_severity_override import EventSeverityOverride
 from app.models.user import User
 
 __all__ = [
@@ -17,4 +18,5 @@ __all__ = [
     "Problem",
     "ProblemEvent",
     "User",
+    "EventSeverityOverride",
 ]