refactor!: CQRS repository split — v0.3.0

FederationRepository (34 methods) → 4 focused traits:
  ActivityRepository  (2)  — idempotency tracking
  FollowRepository    (18) — follower/following graph + migration
  ActorRepository     (6)  — keypairs, remote actor cache, announce tracking
  BlocklistRepository (8)  — domain + actor blocklists

ApObjectHandler (10 methods) → 2 traits:
  ApContentReader  (3) — get_local_objects_for_user/page, count_local_posts
  ApObjectHandler  (9) — all inbox callbacks (on_create, on_mention, etc.)

Builder changes from positional args to named setters:
  ActivityPubService::builder(base_url)
    .activity_repo(arc)
    .follow_repo(arc)
    .actor_repo(arc)
    .blocklist_repo(arc)
    .user_repo(arc)
    .content_reader(arc)
    .object_handler(arc)
    .build()

No behaviour changes.

src/activities/reject.rs

@@ -44,7 +44,7 @@ impl Activity for RejectActivity {
             return Ok(());
         }
         if let Some(user_id) = crate::urls::extract_user_id_from_url(self.object.actor.inner()) {
-            data.federation_repo
+            data.follow_repo
                 .remove_following(user_id, self.actor.inner().as_str())
                 .await?;
         }