fix(deps): declare url crate so digital_human compiles

digital_human.rs uses url::Url::parse but the crate was only a transitive
dependency, not declared in Cargo.toml, so the lib failed to compile with
E0433. Add the explicit dependency (url 2.x was already in Cargo.lock).

Cargo.lock

@@ -427,6 +427,7 @@ dependencies = [
  "tracing",
  "tracing-subscriber",
  "tracing-test",
+ "url",
  "uuid",
  "wiremock",
 ]

Cargo.toml

@@ -27,6 +27,7 @@ sqlx = { version = "0.8", features = [
 
 # HTTP client
 reqwest = { version = "0.12", features = ["stream", "json", "multipart"] }
+url = "2"
 lettre = { version = "0.11", default-features = false, features = ["builder", "hostname", "pool", "rustls-tls", "smtp-transport"] }
 
 # Serialization