Adds blake3 content hashing as the basis for derivative dedup
(thumbnails, HLS) across libraries. Computed inline by the watcher on
ingest and by a new `backfill_hashes` binary for historical rows.
Key changes:
- `content_hash` and `size_bytes` are now populated on new image_exif
rows; a new ExifDao surface (`get_rows_missing_hash`,
`backfill_content_hash`, `find_by_content_hash`) supports backfill and
future hash-keyed lookups.
- The watcher now registers every image/video in image_exif, not just
files with parseable EXIF. EXIF becomes optional enrichment; videos
and other non-EXIF files still get a hashed row. This also makes
DB-indexed sort/filter cover the full library.
- `/image` thumbnail serve dual-looks up hash-keyed path first, then
falls back to the legacy mirrored layout.
- Upload flow accepts `?library=` query param + hashes uploaded files.
- Store_exif logs the underlying Diesel error on insert failure so
constraint violations surface instead of hiding behind a generic
InsertError.
- New migration normalizes rel_path separators to forward slash across
all tables, deduplicating any rows that collide after normalization.
Fixes spurious UNIQUE violations from mixed backslash/forward-slash
paths on Windows ingest.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
