feat: add is_replay flag to execution pipeline and UI

Detect replayed exchanges via X-Cameleer-Replay header during ingestion,
persist the flag through PostgreSQL and OpenSearch, and surface it in
the dashboard (amber replay icon) and exchange detail chain view.

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

@@ -362,6 +362,7 @@ public class OpenSearchIndex implements SearchIndex {
             }).toList());
         }
         map.put("has_trace_data", doc.hasTraceData());
+        map.put("is_replay", doc.isReplay());
         return map;
     }
 
@@ -399,7 +400,8 @@ public class OpenSearchIndex implements SearchIndex {
                 null, // diagramContentHash not stored in index
                 extractHighlight(hit),
                 attributes,
-                Boolean.TRUE.equals(src.get("has_trace_data"))
+                Boolean.TRUE.equals(src.get("has_trace_data")),
+                Boolean.TRUE.equals(src.get("is_replay"))
         );
     }