Allow configuring disk and directory for File attributes

[Huncsuga]

Currently, when using File-type attributes in Lunar, it is possible to define constraints such as minimum and maximum number of files. However, there is no option to configure where these files should be stored.

It would be very useful to allow developers to specify:

• the storage disk (e.g. public, s3, etc.)
• the target directory/path where uploaded files should be saved

This would provide more flexibility and better integration with custom storage setups, especially in projects where different attribute types require different storage strategies.