Fix timestamp creation in log_query_and_results function

app.py

@@ -370,7 +370,7 @@ Return only the JSON object. All key names and string values must be in double q
 def log_query_and_results(query_id: str, query: str, results: list[dict]):
     """Log the query and results to a file."""
     log_entry = {
-        "timestamp": datetime.now().isoformat(),
+        "timestamp": datetime.datetime.now().isoformat(),
         "query_id": query_id,
         "query": query,
         "results": results,