### Description

https://github.com/apache/airflow/pull/17946 implements a `/robots.txt` endpoint to block search engines crawling Airflow - in the cases where it is (accidentally) exposed to the public Internet.

If we record any GET requests to that end-point we'd have a strong warning flag that the deployment is exposed, and could issue a warning in the UI, or even enable some kill-switch on the deployment. 

Some deployments are likely intentionally available and rely on auth mechanisms on the `login` endpoint, so there should be a config option to suppress the warnings.

An alternative approach would be to monitor for requests from specific user-agents used by crawlers for the same reasons

### Use case/motivation

People who accidentally expose airflow have a slightly higher chance of realising they've done so and tighten their security.

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/www/views.py
'url': None,
                    'error': f"can't find dag {dag} or task_id {task_id}",
                }
            )
            response.status_code = 404
            return response
        task = dag.get_task(task_id)
        try:
            url = task.get_extra_links(dttm, link_name)
        except ValueError as err:
            response = jsonify({'url': None, 'error': str(err)})
            response.status_code = 404
            return response
        if url:
            response = jsonify({'error': None, 'url': url})
            response.status_code = 200
            return response
        else:
            response = jsonify({'url': None, 'error': f'No URL found for {link_name}'})
            response.status_code = 404
            return response
    @expose('/object/task_instances')
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def task_instances(self):