feat: progressive multi-round face matching + pending person API

- Identity agent: per-face max matching, multi-round with derived
  seeds from high-confidence faces, angle diversity filter (cosine sim < 0.90)
- Pending person API: POST /file/:file_uuid/pending-person
  + GET /file/:file_uuid/pending-persons with status=pending, source=manual
- Update API docs (07_identity.md)

Cargo.toml

@@ -55,7 +55,7 @@ sqlx = { version = "0.8", features = ["runtime-tokio", "postgres", "sqlite", "js
 mongodb = { version = "2", features = ["tokio-runtime"] }
 bson = { version = "2", features = ["chrono-0_4"] }
 qdrant-client = "1.7"
-reqwest = { version = "0.12", features = ["json", "gzip"] }
+reqwest = { version = "0.12", features = ["json", "gzip", "zstd"] }
 pgvector = { version = "0.3", features = ["sqlx"] }
 
 # HTTP Server