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>

ui/src/api/queries/commands.ts

@@ -83,6 +83,20 @@ export function useUpdateApplicationConfig() {
   })
 }
 
+// ── Processor → Route Mapping ─────────────────────────────────────────────
+
+export function useProcessorRouteMapping(application?: string) {
+  return useQuery({
+    queryKey: ['config', application, 'processor-routes'],
+    queryFn: async () => {
+      const res = await authFetch(`/api/v1/config/${application}/processor-routes`)
+      if (!res.ok) throw new Error('Failed to fetch processor-route mapping')
+      return res.json() as Promise<Record<string, string>>
+    },
+    enabled: !!application,
+  })
+}
+
 // ── Generic Group Command (kept for non-config commands) ──────────────────
 
 interface SendGroupCommandParams {