Handle zero-sized files

[slifty]

Permanent currently has odd behavior with upload attempts for empty files, and it's ultimately rooted in this line: https://github.com/PermanentOrg/upload-service/blob/3617e443ec01e81087ea319cc38461ccd864f810/src/validators/validateCreateFileDestinationUrlParams.ts#L10

Basically: the permanent API awkwardly errors due to the above failed validation if an upload attempt of an empty file happens.

We should either:

1. Change the backend behavior to support empty files! (I'm worried this was a passive decision / bug in the upload service implementation rather than a conscious UX choice)

2. Detect zero size files at the sftp level and return an appropriate error code (currently what happens is an sdk error is thrown because of an unexpected response format)