refactor: move UUID/username routing to application use case — fix handler boundary leak

crates/application/src/use_cases/profile.rs

@@ -23,6 +23,21 @@ pub async fn get_user_by_username(
         .ok_or(DomainError::NotFound)
 }
 
+/// Resolve a path segment that is either a UUID (AP actor URL) or a username.
+pub async fn get_user_by_id_or_username(
+    users: &dyn UserRepository,
+    id_or_username: &str,
+) -> Result<User, DomainError> {
+    if let Ok(uuid) = uuid::Uuid::parse_str(id_or_username) {
+        users
+            .find_by_id(&UserId::from_uuid(uuid))
+            .await?
+            .ok_or(DomainError::NotFound)
+    } else {
+        get_user_by_username(users, id_or_username).await
+    }
+}
+
 pub async fn update_profile(
     users: &dyn UserRepository,
     user_id: &UserId,