fix: enable trackTotalHits for accurate OpenSearch result counts

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/search/OpenSearchIndex.java

@@ -125,6 +125,7 @@ public class OpenSearchIndex implements SearchIndex {
         return org.opensearch.client.opensearch.core.SearchRequest.of(b -> {
             b.index(INDEX_PREFIX + "*")
              .query(buildQuery(request))
+             .trackTotalHits(th -> th.enabled(true))
              .size(size)
              .from(request.offset())
              .sort(s -> s.field(f -> f