feat: image storage generalization, user profile, and federation polish

- Replace PosterStorage with generic ImageStorage port (IMAGE_STORAGE_BACKEND/PATH env vars)
- Rename poster-storage crate to image-storage; serve at /images/{*key}
- Add bio and avatar_path to User model (migration 0009_user_profile)
- update_profile use case with avatar upload, mime validation, old avatar cleanup
- GET/PUT /api/v1/profile and GET/POST /settings/profile HTML page
- Enrich AP Person actor with summary, icon, url, discoverable fields
- Store remote actor avatar_url (migration 0010_ap_remote_actor_avatar)
- Shared inbox delivery via collect_inboxes deduplication
- Broadcast Update(Person) to followers on UserUpdated event
- Paginated outbox: OrderedCollection + OrderedCollectionPage with cursor
- Announce/boost tracking in ap_announces table (migration 0011_ap_announces)

crates/adapters/activitypub-base/src/content.rs

@@ -1,4 +1,5 @@
 use async_trait::async_trait;
+use chrono::{DateTime, Utc};
 use url::Url;
 
 #[async_trait]
@@ -10,6 +11,15 @@ pub trait ApObjectHandler: Send + Sync {
         user_id: uuid::Uuid,
     ) -> anyhow::Result<Vec<(Url, serde_json::Value)>>;
 
+    /// Returns up to `limit` objects ordered newest-first, published before `before`.
+    /// Returns (ap_id, object_json, published_at).
+    async fn get_local_objects_page(
+        &self,
+        user_id: uuid::Uuid,
+        before: Option<DateTime<Utc>>,
+        limit: usize,
+    ) -> anyhow::Result<Vec<(Url, serde_json::Value, DateTime<Utc>)>>;
+
     /// Incoming Create activity — persist remote content.
     async fn on_create(
         &self,