refactor(domain): remove public_key/private_key from User model — managed by federation adapter

crates/domain/src/testing.rs

@@ -771,8 +771,6 @@ impl ActivityPubRepository for TestStore {
             local: false,
             ap_id: Some(actor_ap_url.to_string()),
             inbox_url: None,
-            public_key: None,
-            private_key: None,
             created_at: chrono::Utc::now(),
             updated_at: chrono::Utc::now(),
         };