### 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
try:
            base_date = timezone.parse(request.args["base_date"])
        except (KeyError, ValueError):
            base_date = dag.get_latest_execution_date() or timezone.utcnow()
        dag_runs = (
            session.query(DagRun)
            .filter(DagRun.dag_id == dag.dag_id, DagRun.execution_date <= base_date)
            .order_by(DagRun.execution_date.desc())
            .limit(num_runs)
            .all()
        )
        dag_runs.reverse()
        encoded_runs = [wwwutils.encode_dag_run(dr) for dr in dag_runs]
        dag_run_dates = {dr.execution_date: alchemy_to_dict(dr) for dr in dag_runs}
        max_date = max(dag_run_dates, default=None)
        form = DateTimeWithNumRunsForm(
            data={
                'base_date': max_date or timezone.utcnow(),
                'num_runs': num_runs,
            }
        )
        doc_md = wwwutils.wrapped_markdown(getattr(dag, 'doc_md', None))
        task_log_reader = TaskLogReader()
        if task_log_reader.supports_external_link:
            external_log_name = task_log_reader.log_handler.log_name
        else:
            external_log_name = None
        min_date = min(dag_run_dates, default=None)
        tis = dag.get_task_instances(start_date=min_date, end_date=base_date, session=session)
        data = {