fix: wire DeliveryRequested federation events — outbound AP delivery was broken

FederationEventBridge silently dropped DeliveryRequested events from k-ap,
so no Create/Delete/Accept activities were pushed to follower inboxes.
Reviews only reached remote instances via outbox backfill (pull), and
deletes never propagated.

Bridge now publishes FederationDeliveryRequested domain events through the
event bus; worker calls ap_service.deliver_to_inbox() to send them.

crates/application/src/tests/worker.rs

@@ -57,6 +57,7 @@ impl EventHandler for RecordingHandler {
             }
             DomainEvent::FollowAccepted { .. } => "follow_accepted",
             DomainEvent::BackfillFollower { .. } => "backfill_follower",
+            DomainEvent::FederationDeliveryRequested { .. } => "federation_delivery",
         };
         self.calls.lock().unwrap().push(label);
         Ok(())