feat(api): add GET endpoint for crowd list persons

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Http/Resources/Api/V1/PersonResource.php

@@ -41,6 +41,13 @@ final class PersonResource extends JsonResource
                     ];
                 }
             ),
+            'crowd_list_pivot' => $this->when(
+                $this->pivot && $this->pivot->added_at,
+                fn () => [
+                    'added_at' => $this->pivot->added_at,
+                    'added_by_user_id' => $this->pivot->added_by_user_id,
+                ]
+            ),
             'tags' => $this->when(
                 $this->user_id && $this->relationLoaded('user'),
                 function () {