refactor: remove SocialQueryPort — replaced by SocialQuery + FederationAdminQuery

-319 lines. Legacy SocialQueryPort trait, NoopSocialQueryPort,
PanicSocialQueryPort all deleted. Federation repos now implement
FederationAdminQuery (single method). get_users uses FederationAdminQuery.
All other consumers use unified SocialQuery.

crates/application/src/diary/tests/get_activity_feed.rs

@@ -116,11 +116,6 @@ impl domain::ports::SocialQuery for FakeSocialWithFollowing {
     ) -> Result<Vec<String>, DomainError> {
         Ok(self.0.clone())
     }
-    async fn list_all_followed_remote_actors(
-        &self,
-    ) -> Result<Vec<domain::models::RemoteActorInfo>, DomainError> {
-        Ok(vec![])
-    }
 }
 
 #[tokio::test]