Add Postman collection generation to setup-project.sh

[PAMulligan]

Description

Generate a Postman collection as part of the project setup that includes the initial health check endpoint and a collection structure ready for API development.

Why

Postman is one of the most popular tools for API development and testing. Including a starter collection means developers can immediately import it and start testing their API without manually creating requests.

Acceptance Criteria

• Generate a `postman/collection.json` file during `setup-project.sh`
• Include:
  • Health check request (`GET /health`)
  • Root endpoint request (`GET /`)
  • Environment variables (base_url, auth_token)
  • Collection structure with folders (Health, Auth, Resources)
  • Pre-request scripts for auth token injection
• Generate a `postman/environment.json` for local development
• Update `generate-openapi-docs.sh` to also regenerate the Postman collection from the current OpenAPI spec
• Add export instructions in generated project README
• CI passes