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/adapters/activitypub/src/lib.rs

@@ -33,7 +33,7 @@ pub type FederationRepos = (
     std::sync::Arc<dyn FollowRepository>,
     std::sync::Arc<dyn ActorRepository>,
     std::sync::Arc<dyn BlocklistRepository>,
-    std::sync::Arc<dyn domain::ports::SocialQueryPort>,
+    std::sync::Arc<dyn domain::ports::FederationAdminQuery>,
     std::sync::Arc<dyn RemoteReviewRepository>,
     std::sync::Arc<dyn domain::ports::RemoteWatchlistRepository>,
 );