chore: gate test helpers, code style, stricter clippy

crates/domain/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "domain"
 version = "0.1.0"
-edition = "2024"
+edition.workspace = true
 
 [dependencies]
 uuid = { workspace = true }

crates/domain/src/lib.rs

@@ -5,5 +5,5 @@ pub mod ports;
 pub mod services;
 pub mod value_objects;
 
-#[cfg(any(test, feature = "test-helpers"))]
+#[cfg(feature = "test-helpers")]
 pub mod testing;