Adds a 64-bit dHash perceptual hash (internal/imagehash, built on the existing
disintegration/imaging — no new dependency) and starts populating the long-unused
data.files.phash column:
- Upload sets phash inline for images (cheap, from the in-memory bytes).
- Replace recomputes it from new content for images and clears it for anything
else, so a stale hash never survives a content swap.
- FileRepo.SetPHash sets/clears the hash (used by Replace and, later, the dedup
backfill).
- DiskStorage.VideoFrameMiddle extracts a frame from the middle of a clip
(ffprobe duration -> ffmpeg -ss duration/2), avoiding the shared-intro collision
a fixed early offset causes. It is a concrete method, not part of the storage
port: only the dedup CLI needs it, keeping ffmpeg off the upload path. Video
phashes are therefore computed by that CLI, not at upload time.
- DUPLICATE_HASH_THRESHOLD config (default 10/64) for the later pair rescan.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
