Skip staff entries without names

[Weegley]

Summary

Skip Kinopoisk staff entries that do not contain either a Russian or English name.

Jellyfin rejects PersonInfo objects with an empty Name, which currently causes metadata refreshes to fail with:

The value cannot be an empty string. (Parameter 'person.Name')

Changes

• Filter out staff entries with empty or whitespace-only names.
• Keep valid Russian and English fallback names.
• Preserve person sort order after filtering.
• Add a regression test.

Testing

• All 13 automated tests pass.