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/repository.rs

@@ -21,6 +21,7 @@ pub struct RemoteActor {
     pub inbox_url: String,
     pub shared_inbox_url: Option<String>,
     pub display_name: Option<String>,
+    pub avatar_url: Option<String>,
 }
 
 #[derive(Debug, Clone)]
@@ -88,4 +89,12 @@ pub trait FederationRepository: Send + Sync {
         remote_actor_url: &str,
         status: FollowingStatus,
     ) -> Result<()>;
+    async fn add_announce(
+        &self,
+        activity_id: &str,
+        object_url: &str,
+        actor_url: &str,
+        announced_at: chrono::DateTime<chrono::Utc>,
+    ) -> Result<()>;
+    async fn count_announces(&self, object_url: &str) -> Result<usize>;
 }