feat(config): support human-readable durations with legacy compatibility

wakey-agent/Cargo.toml

@@ -9,6 +9,7 @@ anyhow = "1"
 clap = { version = "4", features = ["derive"] }
 futures-util = "0.3"
 http = "1"
+humantime-serde = "1"
 macaddr = { version = "1", features = ["serde", "serde_std"] }
 nix = { version = "0.31", default-features = false, features = [
     "signal",