refactor: remove diagramNodeId indirection, use processorId directly

Agent now uses Camel processorId as RouteNode.id, eliminating the
nodeId mapping layer. Drop diagram_node_id column (V6 migration),
remove from ProcessorRecord/ProcessorNode/IngestionService/DetailService,
add /processor-routes endpoint for processorId→routeId lookup,
simplify frontend diagram-mapping and ExchangeDetail overlays,
replace N diagram fetches in AppConfigPage with single hook.

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

cameleer3-server-app/src/main/resources/db/migration/V6__drop_diagram_node_id.sql

@@ -0,0 +1 @@
+ALTER TABLE processor_executions DROP COLUMN IF EXISTS diagram_node_id;