fix: address remaining 3 NOT DONE plan items

#18 featured collection: add featured_url to ApUser/DbActor/Person;
     serialized as featured field in AP JSON when set by consumer.

#19 Tombstone in Delete: broadcast_delete_to_followers now sends
     {"type":"Tombstone","id":"..."} instead of bare URL string.

#21 Backfill pagination: run_backfill uses get_local_objects_page
     with cursor-based loop — avoids loading all posts into memory;
     delivers newest-to-oldest in BATCH_SIZE chunks.

src/actors.rs

@@ -39,6 +39,7 @@ pub struct DbActor {
     pub attachment: Vec<ApProfileField>,
     pub manually_approves_followers: bool,
     pub actor_type: ApActorType,
+    pub featured_url: Option<Url>,
 }
 
 #[derive(Debug, Clone, Deserialize, Serialize)]
@@ -100,6 +101,8 @@ pub struct Person {
     also_known_as: Vec<String>,
     #[serde(skip_serializing_if = "Vec::is_empty", default)]
     attachment: Vec<ProfileFieldObject>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    featured: Option<Url>,
 }
 
 struct ActorUrls {
@@ -189,6 +192,7 @@ pub async fn get_local_actor(
         attachment: user.attachment,
         manually_approves_followers: user.manually_approves_followers,
         actor_type: user.actor_type,
+        featured_url: user.featured_url,
     })
 }
 
@@ -264,6 +268,7 @@ impl Object for DbActor {
             attachment: user.attachment,
             manually_approves_followers: user.manually_approves_followers,
             actor_type: user.actor_type,
+            featured_url: user.featured_url,
         }))
     }
 
@@ -316,6 +321,7 @@ impl Object for DbActor {
             image,
             also_known_as,
             attachment,
+            featured: self.featured_url,
         })
     }
 
@@ -399,6 +405,7 @@ impl Object for DbActor {
                 .collect(),
             manually_approves_followers: json.manually_approves_followers,
             actor_type: json.kind,
+            featured_url: json.featured,
         })
     }
 }

src/service/backfill.rs

@@ -78,12 +78,27 @@ impl ActivityPubService {
         let data = config.to_request_data();
         let local_actor = get_local_actor(owner_user_id, &data).await.map_err(|e| anyhow::anyhow!("{e}"))?;
         let inbox = Url::parse(&follower_inbox_url)?;
-        let mut objects = data.object_handler.get_local_objects_for_user(owner_user_id).await?;
-        objects.reverse();
-        let total = objects.len();
-        let (mut success_count, mut failure_count) = (0usize, 0usize);
-        for chunk in objects.chunks(BATCH_SIZE) {
-            for (ap_id, object_json) in chunk {
+
+        // Cursor-based pagination via get_local_objects_page (newest-first).
+        // Avoids loading the entire post history into memory at once.
+        let mut before: Option<chrono::DateTime<chrono::Utc>> = None;
+        let (mut success_count, mut failure_count, mut total) = (0usize, 0usize, 0usize);
+
+        loop {
+            let page = data
+                .object_handler
+                .get_local_objects_page(owner_user_id, before, BATCH_SIZE)
+                .await?;
+
+            if page.is_empty() {
+                break;
+            }
+
+            let is_last_page = page.len() < BATCH_SIZE;
+            // Advance cursor to the oldest timestamp in this page.
+            before = page.last().map(|(_, _, ts)| *ts);
+
+            for (ap_id, object_json, _ts) in &page {
                 let create_id = Url::parse(&format!(
                     "{}/activities/create/{}",
                     base_url,
@@ -94,16 +109,35 @@ impl ActivityPubService {
                     actor: ObjectId::from(local_actor.ap_id.clone()),
                     object: object_json.clone(), to: vec![], cc: vec![], bto: vec![], bcc: vec![],
                 };
-                let sends = SendActivityTask::prepare(&WithContext::new_default(create), &local_actor, vec![inbox.clone()], &data).await?;
+                let sends = SendActivityTask::prepare(
+                    &WithContext::new_default(create),
+                    &local_actor,
+                    vec![inbox.clone()],
+                    &data,
+                ).await?;
+                total += 1;
                 if send_with_retry(sends, &data, max_attempts, initial_delay).await.is_empty() {
                     success_count += 1;
                 } else {
                     failure_count += 1;
                 }
             }
+
+            if is_last_page {
+                break;
+            }
+
             tokio::time::sleep(std::time::Duration::from_millis(super::BATCH_FETCH_SLEEP_MS)).await;
         }
-        tracing::info!(user_id = %owner_user_id, follower = %follower_inbox_url, sent = success_count, failed = failure_count, total = total, "backfill complete");
+
+        tracing::info!(
+            user_id = %owner_user_id,
+            follower = %follower_inbox_url,
+            sent = success_count,
+            failed = failure_count,
+            total = total,
+            "backfill complete"
+        );
         Ok(())
     }
 }

src/service/broadcast.rs

@@ -119,7 +119,7 @@ impl ActivityPubService {
             id: activity_url(&self.base_url).map_err(|e| anyhow::anyhow!("{e}"))?,
             kind: Default::default(),
             actor: ObjectId::from(local_actor.ap_id.clone()),
-            object: serde_json::json!(ap_id.to_string()),
+            object: serde_json::json!({"type": "Tombstone", "id": ap_id.to_string()}),
             to: vec![crate::urls::AS_PUBLIC.to_string()],
             cc: vec![local_actor.followers_url.to_string()],
         };

src/tests/actors.rs

@@ -34,6 +34,7 @@ fn person_serializes_with_enriched_fields() {
         image: None,
         also_known_as: vec![],
         attachment: vec![],
+        featured: Some("https://example.com/users/1/featured".parse().unwrap()),
     };
     let json = serde_json::to_value(&person).unwrap();
     assert_eq!(json["discoverable"], true);

src/user.rs

@@ -58,6 +58,9 @@ pub struct ApUser {
     pub manually_approves_followers: bool,
     /// AP actor type serialized in the actor JSON. Defaults to `Person`.
     pub actor_type: ApActorType,
+    /// URL of the `featured` (pinned posts) collection. Set to expose a pinned
+    /// posts collection in the actor JSON, compatible with Mastodon/Pleroma.
+    pub featured_url: Option<Url>,
 }
 
 #[async_trait]