feat(web): restore payload CMS (cuidecar pattern + importMap)

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

apps/broker/src/neo4j-client.ts

@@ -0,0 +1,22 @@
+import neo4j from "neo4j-driver";
+import { env } from "./env";
+
+export const neo4jDriver = neo4j.driver(
+  env.NEO4J_URL,
+  neo4j.auth.basic(env.NEO4J_USER, env.NEO4J_PASSWORD),
+);
+
+export function meshDbName(meshId: string): string {
+  return `mesh_${meshId.toLowerCase().replace(/[^a-z0-9]/g, "")}`;
+}
+
+export async function ensureDatabase(name: string): Promise<void> {
+  const session = neo4jDriver.session({ database: "system" });
+  try {
+    await session.run(`CREATE DATABASE $name IF NOT EXISTS`, { name });
+  } catch {
+    /* may not support multi-db in community edition — fall back to default */
+  } finally {
+    await session.close();
+  }
+}