Guard upload progress when total size is unknown

[zerox80]

Summary

• avoid invalid progress percentages when upload size is unknown or zero
• clamp calculated upload progress to the valid 0 to 100 range
• apply the same behavior to filesystem and content URI uploads

Tests

• Added unit coverage for zero, unknown, normal, and over-complete progress values

[guruz]

This is for uploads? In which case would the size be not known by us?

[zerox80]

Yes, this is upload progress. In the current worker flow we should normally know the size: filesystem uploads use File.length(), content URI uploads are copied to a cache file first and then use that cached file length, and TUS sends Upload-Length. Core also requires Upload-Length for TUS creation, so unknown size is not an expected OpenCloud upload path.

The <=0 guard is mainly defensive for invalid progress callback totals / zero-size edge cases. The practical fix here is also clamping over-complete values to 100.

[zerox80]

backend / reva sends 412 if file size unknown, so this PR can be closed