feat(user): add given_name/family_name auth.users

reflect OIDC
  schema migration, User entity additions, and three defense-in-depth gaps closed, with all 280 unit tests and 13 Hurl files green
  infrastructure (lettre + EmailSender port).

  - Migration migrations/20260612000003_users_username_email_login.sql — adds nullable given_name/family_name columns to auth.users.
  - User entity (src/domain/entities/user.rs) — has_login_credential() placeholder-check encapsulation, set_username revalidating setter, given/family-name fields + getters/setters, validate_username widened 32→254 and now accepts email shape.
  from_data_full extended with two new params; all 7 callsites in user_pg_repository.rs updated.
  - Schema-side legacy guards (src/application/services/auth_application_service.rs) — bumped the duplicated 32-char check in setup_create_admin and admin_create_user to 254 to match.
  - Gap #1 (subject_group_service.rs) — add_member now rejects external candidates with an audit-logged AccessDenied. Service gained an Arc<UserPgRepository> field, wired through DI. New integration test test_external_user_cannot_be_added_as_member.
  - Gap #2 (user_repository.rs + auth_ports.rs + user_pg_repository.rs) — list_users/search_users gained an include_external: bool param defaulting effectively to false everywhere internal-user-facing. auth_application_service exposes a new
  list_users_including_external for the admin surface.
  - Gap #3 (pg_acl_engine.rs) — expand_user now SELECTs is_external and skips INTERNAL_GROUP_ID for externals; defaults to is_external=true on missing user to fail closed.

src/application/ports/auth_ports.rs

@@ -91,11 +91,25 @@ pub trait UserStoragePort: Send + Sync + 'static {
         usage_bytes: i64,
     ) -> Result<(), DomainError>;
 
-    /// Lists users with pagination
-    async fn list_users(&self, limit: i64, offset: i64) -> Result<Vec<User>, DomainError>;
+    /// Lists users with pagination. `include_external` defaults to `false`
+    /// at every call site that surfaces users to other internal users
+    /// (autocomplete, sharee search, etc.); only the admin management UI
+    /// passes `true`. See [`UserRepository::list_users`] for the rationale.
+    async fn list_users(
+        &self,
+        limit: i64,
+        offset: i64,
+        include_external: bool,
+    ) -> Result<Vec<User>, DomainError>;
 
     /// Searches users by username or email (SQL ILIKE) with a limit.
-    async fn search_users(&self, query: &str, limit: i64) -> Result<Vec<User>, DomainError>;
+    /// See [`list_users`] for the meaning of `include_external`.
+    async fn search_users(
+        &self,
+        query: &str,
+        limit: i64,
+        include_external: bool,
+    ) -> Result<Vec<User>, DomainError>;
 
     /// Lists users by role (e.g., "admin" or "user")
     async fn list_users_by_role(&self, role: &str) -> Result<Vec<User>, DomainError>;