docs: add healthcheck example

[HsukqiLee]

Summary

Add an HTTP healthcheck to the Quick Start Compose example.

The example checks the web service on port 5000 every 30 seconds and documents that curl must be available in the web image.

Fixes #14160

Validation

• git diff --check passed.
• docker compose config was checked against the healthcheck snippet.
• The full documentation validation was not run because the local environment lacks the repository documentation build prerequisites.

AI Disclosure

This contribution was prepared with assistance from OpenCode using the gpt-5.6-sol model. The human submitter reviewed the resulting changes and validation details before submission.