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>

frontend/src/version.ts

@@ -1,4 +1,4 @@
 /** Fallback до загрузки /health; при релизе держите в sync с backend/app/version.py */
 export const APP_NAME = "Security Alert Center";
-export const APP_VERSION = "0.3.7";
+export const APP_VERSION = "0.3.8";
 export const APP_VERSION_LABEL = `${APP_NAME} v.${APP_VERSION}`;