fix: fetch_actor_urls_from_collection follows 'first' page link like outbox does

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

@@ -1622,7 +1622,8 @@ impl domain::ports::FederationActionPort for ActivityPubService {
         &self,
         collection_url: &str,
     ) -> Result<Vec<String>, domain::errors::DomainError> {
-        let resp: serde_json::Value = reqwest::Client::new()
+        let client = reqwest::Client::new();
+        let base: serde_json::Value = client
             .get(collection_url)
             .header("Accept", "application/activity+json, application/ld+json")
             .send()
@@ -1632,8 +1633,27 @@ impl domain::ports::FederationActionPort for ActivityPubService {
             .await
             .map_err(|e| domain::errors::DomainError::ExternalService(e.to_string()))?;
 
+        // Base collections typically have no orderedItems — follow the `first` page link.
+        let page = if base["orderedItems"].is_null() {
+            if let Some(first_url) = base["first"].as_str() {
+                client
+                    .get(first_url)
+                    .header("Accept", "application/activity+json, application/ld+json")
+                    .send()
+                    .await
+                    .map_err(|e| domain::errors::DomainError::ExternalService(e.to_string()))?
+                    .json()
+                    .await
+                    .map_err(|e| domain::errors::DomainError::ExternalService(e.to_string()))?
+            } else {
+                base
+            }
+        } else {
+            base
+        };
+
         let empty = vec![];
-        let items = resp["orderedItems"].as_array().unwrap_or(&empty);
+        let items = page["orderedItems"].as_array().unwrap_or(&empty);
         Ok(items
             .iter()
             .filter_map(|v| v.as_str().map(|s| s.to_string()))