fix: hide ????????? after session terminate (0.3.8)

Persist session_terminated in event details, expose in API, and update Events/Dashboard UI.

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

backend/app/services/event_summary.py

@@ -3,6 +3,7 @@ from sqlalchemy.orm import Session
 from app.models.event import Event
 from app.schemas.list_models import EventSummary
 from app.services.event_actor_user import extract_event_actor_user
+from app.services.host_sessions import event_session_terminated
 from app.services.rdg_display import build_rdg_display
 from app.services.rdg_session_flap import resolve_rdg_flap_summary
 
@@ -48,4 +49,5 @@ def event_to_summary(event: Event, db: Session | None = None) -> EventSummary:
         rdg_flap_qwinsta_event_id=rdg_flap_qwinsta_event_id,
         rdg_access_path=rdg_access_path,
         rdg_qwinsta_enabled=rdg_qwinsta_enabled,
+        session_terminated=event_session_terminated(event),
     )