feat: implement remote unfollow — wire FederationActionPort through delete_follow handler

crates/application/src/use_cases/social.rs

@@ -137,6 +137,27 @@ pub async fn follow_user(
     Ok(())
 }
 
+pub async fn unfollow_actor(
+    follows: &dyn FollowRepository,
+    users: &dyn UserRepository,
+    federation: &dyn FederationActionPort,
+    events: &dyn EventPublisher,
+    follower_id: &UserId,
+    username: &str,
+) -> Result<(), DomainError> {
+    if username.contains('@') {
+        federation.unfollow_remote(follower_id, username).await
+    } else {
+        let uname = Username::new(username)
+            .map_err(|_| DomainError::InvalidInput("invalid username".into()))?;
+        let target = users
+            .find_by_username(&uname)
+            .await?
+            .ok_or(DomainError::NotFound)?;
+        unfollow_user(follows, events, follower_id, &target.id).await
+    }
+}
+
 pub async fn unfollow_user(
     follows: &dyn FollowRepository,
     events: &dyn EventPublisher,
@@ -370,6 +391,48 @@ mod tests {
         assert!(store.follows.lock().unwrap().is_empty());
     }
 
+    #[tokio::test]
+    async fn unfollow_actor_local_routes_to_unfollow_user() {
+        let store = TestStore::default();
+        let alice = user("alice");
+        let bob = user("bob");
+        store.users.lock().unwrap().push(bob.clone());
+        // Create an existing follow first
+        store
+            .follows
+            .lock()
+            .unwrap()
+            .push(domain::models::social::Follow {
+                follower_id: alice.id.clone(),
+                following_id: bob.id.clone(),
+                state: domain::models::social::FollowState::Accepted,
+                ap_id: None,
+                created_at: chrono::Utc::now(),
+            });
+        unfollow_actor(&store, &store, &store, &store, &alice.id, "bob")
+            .await
+            .unwrap();
+        assert!(store.follows.lock().unwrap().is_empty());
+    }
+
+    #[tokio::test]
+    async fn unfollow_actor_remote_routes_to_federation() {
+        let store = TestStore::default();
+        let alice = user("alice");
+        unfollow_actor(
+            &store,
+            &store,
+            &store,
+            &store,
+            &alice.id,
+            "@bob@example.com",
+        )
+        .await
+        .unwrap();
+        // TestStore.unfollow_remote is a no-op — just verify it doesn't error
+        assert!(store.follows.lock().unwrap().is_empty());
+    }
+
     #[tokio::test]
     async fn boost_and_unboost() {
         let store = TestStore::default();