ANW-11 vault scanner: walk, parse frontmatter, compute ETag

Cargo.toml

@@ -15,6 +15,7 @@ path = "src/main.rs"
 anyhow = "1"
 axum = "0.8"
 blake3 = "1"
+chrono = { version = "0.4", default-features = false, features = ["std"] }
 clap = { version = "4", features = ["derive", "env"] }
 hydra = "0.1"
 notify = "8"
@@ -28,6 +29,10 @@ tower = "0.5"
 tower-http = { version = "0.6", features = ["trace"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+walkdir = "2"
+
+[dev-dependencies]
+tempfile = "3"
 
 [lints.rust]
 unsafe_code = "forbid"