feat(express): enable API docs for ping endpoint

Add express_entry.ts to control OpenAPI doc generation. Starting with
ping endpoint only to validate the pipeline before adding more.

WP-7280

TICKET: WP-7280

Author: derranW26

modules/express/src/typedRoutes/api/common/ping.ts

@@ -5,6 +5,18 @@ import { BitgoExpressError } from '../../schemas/error';
 /**
  * Ping
  *
+ * Health check endpoint for BitGo Express. Use this endpoint to verify that the
+ * Express server is running and responsive before making other API calls.
+ *
+ * Common use cases:
+ * - Load balancer health checks
+ * - Container orchestration liveness probes (Kubernetes, ECS)
+ * - Monitoring and alerting systems
+ * - Pre-flight connectivity validation from client applications
+ *
+ * This endpoint requires no authentication and returns an empty 200 response
+ * when the service is operational.
+ *
  * @operationId express.ping
  * @tag express
  */