fix: harden Polygon operation validation

site/routes/run.py

@@ -50,6 +50,9 @@ def run_operation(uid):
     if op.get("dtFinish") is not None:
         return jsonify({"error": "operation already completed"}), 409
 
+    if not state.get_instance(op.get("instanceUid")):
+        return jsonify({"error": "instance not found"}), 404
+
     # Фиксируем время старта
     op["dtStart"] = _now()