feat: implement remote unfollow — wire FederationActionPort through delete_follow handler

crates/domain/src/ports.rs

@@ -223,6 +223,11 @@ pub trait RemoteActorConnectionRepository: Send + Sync {
 pub trait FederationActionPort: Send + Sync {
     async fn lookup_actor(&self, handle: &str) -> Result<RemoteActor, DomainError>;
     async fn follow_remote(&self, local_user_id: &UserId, handle: &str) -> Result<(), DomainError>;
+    async fn unfollow_remote(
+        &self,
+        local_user_id: &UserId,
+        handle: &str,
+    ) -> Result<(), DomainError>;
     async fn actor_json(&self, user_id: &UserId) -> Result<String, DomainError>;
     async fn followers_collection_json(
         &self,