duplicates: perceptual hash + soft-mark resolution + upload 409

Adds pHash + dHash columns alongside the existing blake3 content_hash so
near-duplicates (re-encoded, resized, format-converted copies) become
queryable. /duplicates/{exact,perceptual} return groups; /duplicates/
{resolve,unresolve} flip a duplicate_of_hash soft-mark on losing rows
and union perceptual-only tag sets onto the survivor. The default
/photos listing filters duplicate_of_hash IS NULL so demoted siblings
stop cluttering the grid; include_duplicates=true opts back in for
Apollo's review modal. Upload now hashes bytes pre-write and returns
409 with the canonical sibling when a file's bytes already exist.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -59,5 +59,7 @@ ical = "0.11"
 scraper = "0.20"
 base64 = "0.22"
 blake3 = "1.5"
+image_hasher = "3.0"
+bk-tree = "0.5"
 async-trait = "0.1"
 indicatif = "0.17"