fix: register JavaTimeModule on ObjectMapper for processors_json serialization

The ObjectMapper used to serialize the processor tree to JSON lacked
JavaTimeModule, causing Instant fields (startTime, endTime) to fail
silently — processors_json was always null.

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

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

@@ -3,6 +3,7 @@ package com.cameleer3.server.core.ingestion;
 import com.cameleer3.common.model.ExchangeSnapshot;
 import com.cameleer3.common.model.ProcessorExecution;
 import com.cameleer3.common.model.RouteExecution;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import com.cameleer3.server.core.indexing.ExecutionUpdatedEvent;
 import com.cameleer3.server.core.storage.DiagramStore;
 import com.cameleer3.server.core.storage.ExecutionStore;
@@ -19,7 +20,9 @@ import java.util.function.Consumer;
 
 public class IngestionService {
 
-    private static final ObjectMapper JSON = new ObjectMapper();
+    private static final ObjectMapper JSON = new ObjectMapper()
+            .findAndRegisterModules()
+            .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
 
     private final ExecutionStore executionStore;
     private final DiagramStore diagramStore;