Include 'id' in WebBrokerApi delete success response

[coderabbitai]

Summary

The DeleteWebBrokerApiById handler in gateway/gateway-controller/pkg/api/handlers/webbroker_api_handler.go currently returns only status and message in the HTTP 200 delete response. The documented schema for this endpoint includes the id of the deleted resource.

Expected

The delete success response should include the id field to match the endpoint contract:

{
  "status": "success",
  "message": "WebBrokerApi deleted successfully",
  "id": "<deleted-resource-id>"
}

Context

• Identified in PR: Add implementation for WebBrokerAPIs #1954 (comment)
• Related improvements tracked in: [DO NOT MERGE] Add Implementation for Exposing Brokers as Subscribable APIs over Web-friendly Protocols #1944

Requested by: @senthuran16