Frontend web page, upload files can not save to current work dir

[yifenglong-dev]

Version:
aioncore-v0.1.30

problem:
User uploads a file (by dragging and dropping, pasting, or clicking the attachment button)
│
▼
front-end call POST /api/fs/upload（multipart）
│
▼
backend FileService::create_upload_file()
│
▼
❌ Hard coding uses std::env::temp_dir() as the storage path
│ → <temp_dir>/aionui/<conversation_id>/
│ → or <temp_dir>/aionui/general/

Expect:
Upload files and save them to the current working directory

Actual:
Uploaded file save to <temp_dir>/aionui/<conversation_id>/