prevent cache

app.py

@@ -221,7 +221,12 @@ def preview_video(file_id):
         if not os.path.exists(output_path):
             return jsonify({'error': 'File not found'}), 404
         
-        return send_file(output_path, mimetype='video/mp4')
+        response = send_file(output_path, mimetype='video/mp4')
+        # Prevent caching
+        response.headers['Cache-Control'] = 'no-store, no-cache, must-revalidate, max-age=0'
+        response.headers['Pragma'] = 'no-cache'
+        response.headers['Expires'] = '0'
+        return response
     except Exception as e:
         return jsonify({'error': str(e)}), 500