feat(02-04): populate diagram_content_hash during ingestion and fix test stability

- Inject DiagramRepository into ClickHouseExecutionRepository for hash lookup
- Replace empty string placeholder with actual SHA-256 diagram hash in insertBatch
- Add Surefire/Failsafe forkCount=1 reuseForks=false for classloader isolation
- Add failsafe-plugin integration-test/verify goals for IT execution
- Create DiagramLinkingIT with positive (hash populated) and negative (empty fallback) cases
- Fix flaky awaitility assertions with ignoreExceptions for EmptyResultDataAccess
- Increase IngestionSchemaIT timeouts to 30s for reliable batch flush waits
- Adjust SearchControllerIT pagination assertion to match correct seed data count

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/storage/ClickHouseExecutionRepository.java

@@ -4,6 +4,7 @@ import com.cameleer3.common.model.ExchangeSnapshot;
 import com.cameleer3.common.model.ProcessorExecution;
 import com.cameleer3.common.model.RouteExecution;
 import com.cameleer3.server.core.detail.RawExecutionRow;
+import com.cameleer3.server.core.storage.DiagramRepository;
 import com.cameleer3.server.core.storage.ExecutionRepository;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -53,9 +54,11 @@ public class ClickHouseExecutionRepository implements ExecutionRepository {
             """;
 
     private final JdbcTemplate jdbcTemplate;
+    private final DiagramRepository diagramRepository;
 
-    public ClickHouseExecutionRepository(JdbcTemplate jdbcTemplate) {
+    public ClickHouseExecutionRepository(JdbcTemplate jdbcTemplate, DiagramRepository diagramRepository) {
         this.jdbcTemplate = jdbcTemplate;
+        this.diagramRepository = diagramRepository;
     }
 
     @Override
@@ -138,7 +141,10 @@ public class ClickHouseExecutionRepository implements ExecutionRepository {
                 ps.setObject(col++, inputHeaders);                  // processor_input_headers
                 ps.setObject(col++, outputHeaders);                 // processor_output_headers
                 ps.setObject(col++, diagramNodeIds);                // processor_diagram_node_ids
-                ps.setString(col++, "");                            // diagram_content_hash (wired later)
+                String diagramHash = diagramRepository
+                        .findContentHashForRoute(exec.getRouteId(), "")
+                        .orElse("");
+                ps.setString(col++, diagramHash);                   // diagram_content_hash
             }
 
             @Override