Add Frontend Track Events

What does this MR do and why?

Adds frontend tracking events for AI Catalog agents and flows to track when users view the index page and individual item details.

References

Related to #556791 (closed)

Screenshots or screen recordings

No visual changes, but a demo:

output

How to set up and validate locally

1. Enable the feature flag: echo "Feature.enable(:global_ai_catalog)" | rails c
2. Add some seed data: https://gitlab.com/gitlab-org/ai-powered/workflow-catalog/team-tasks/-/wikis/Setting-up-GDK-for-Workflow-Catalog-Development#seed-data
3. Visit http://gdk.test:3000/explore/ai-catalog/agents
4. Verify tracking events are fired:
   • view_ai_catalog_item_index when viewing the list page
   • view_ai_catalog_item when viewing individual item details
5. Use the internal events monitor to verify events:

   rails runner scripts/internal_events/monitor.rb view_ai_catalog_item_index view_ai_catalog_item

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #556791 (closed)