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/schemas/list_models.py

@@ -83,6 +83,7 @@ class EventSummary(BaseModel):
     rdg_flap_qwinsta_event_id: int | None = None
     rdg_access_path: str | None = None
     rdg_qwinsta_enabled: bool = False
+    session_terminated: bool = False
 
     model_config = {"from_attributes": True}