A background Fingerprinter runs after every scan and at startup, one file
at a time, filling media_files.sha256 and track_fingerprints (fpcalc raw,
first 120 s). Without fpcalc only SHA-256 is computed and files stay
queued for Chromaprint. Changing a file's content resets its prints.
Similarity() compares raw prints with a ±80-point alignment search; it is
the basis for duplicate detection in the upload queue.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
