feat: add session expiry warning

backend/workflows/views.py

@@ -138,6 +138,22 @@ def mark_all_notifications_read(request):
     UserNotification.objects.filter(user=request.user, read_at__isnull=True).update(read_at=timezone.now())
     return _redirect_back(request, 'home')
 
+
+@login_required
+@require_POST
+def session_keepalive(request):
+    now_ts = int(timezone.now().timestamp())
+    request.session['last_activity_ts'] = now_ts
+    request.session['auth_fresh_ts'] = now_ts
+    return JsonResponse(
+        {
+            'status': 'ok',
+            'idle_timeout_seconds': settings.SESSION_IDLE_TIMEOUT_SECONDS,
+            'reauth_timeout_seconds': settings.SENSITIVE_ACTION_REAUTH_SECONDS,
+            'refreshed_at': now_ts,
+        }
+    )
+
 def healthz(request):
     db_ok = True
     try: