fix: Add output buffer cleansing in Response::json and enhance error logging for conversation parsing

backend/app/Core/Response.php

@@ -54,7 +54,11 @@ class Response
         $this->sendHeaders();
         http_response_code($this->statusCode);
 
-        echo json_encode($data, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
+        if (ob_get_length()) {
+            ob_clean();
+        }
+
+        echo json_encode($data, JSON_UNESCAPED_UNICODE);
         exit;
     }