fix: align server with protocol v2 chunked transport spec

- ChunkIngestionController: /data/chunks → /data/executions (matches
  PROTOCOL.md endpoint the agent actually posts to)
- ExecutionController: conditional on ClickHouse being disabled to
  avoid mapping conflict
- Persist originalExchangeId and replayExchangeId from ExecutionChunk
  envelope through to ClickHouse (was silently dropped)
- V5 migration adds the two new columns to executions table

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

cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/ChunkAccumulator.java

@@ -168,7 +168,9 @@ public class ChunkAccumulator {
                 envelope.getTraceId(),
                 envelope.getSpanId(),
                 false,  // hasTraceData — not tracked at envelope level
-                envelope.getReplayExchangeId() != null  // isReplay
+                envelope.getReplayExchangeId() != null,  // isReplay
+                envelope.getOriginalExchangeId(),
+                envelope.getReplayExchangeId()
         );
     }
 

cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/MergedExecution.java

@@ -35,5 +35,7 @@ public record MergedExecution(
         String traceId,
         String spanId,
         boolean hasTraceData,
-        boolean isReplay
+        boolean isReplay,
+        String originalExchangeId,
+        String replayExchangeId
 ) {}