scan.py used scalar_one_or_none() to test whether any other photo
shared the same file_hash, but that helper raises MultipleResultsFound
the moment 2+ rows match — i.e. exactly the duplicate case it was
trying to flag. Every file beyond the second copy bombed out with
"Multiple rows were found when one or none was required" and was
left in the failed bucket. Replace with a COUNT(*) > 0 check.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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