Potential a slip of a pen: store settings in server while using single-user mode?

### Expected Behavior

Settings should be stored in localstorage when using single-user mode

### Actual Behavior

Backend never let frontend store settings in localstorage

### Steps to Reproduce

none

### Debug Logs

```powershell
none
```

### Other

I noticed that frontend of ComfyUI supports store settings in localstorage(`browser mode` in comfyui's definations), however, i did not find any cases that backend let frontend use localstorage mode.

I suppose this may be a slip of a pen: settings should be stored in localstorage when using single-user mode, if not, if one user change his settings, this will be applied to all users' behaviours, may be unreasonable.

If this is comfirmed to be a small error, i have committed some changes.