Upgraded memory management for large file transfers

Memory management completely upgraded. Managing and transferring thousands to tens of thousands of files was quite difficult in terms of memory management. Handling a few hundred was easy, but processing tens of thousands simultaneously puts a significant strain on the system. To improve this, we enhanced file session management. We replaced the existing vector-based system with a map-based one, and for objects with delays like file writing, we implemented an async delete function for delayed deletion.