Handling of the DagRun callback log should be visible on the UI somewhere

### Description

When a DagRun handles its callbacks, the logs are only available in the DAGFileProcessorProcess log location. I want to be able to view these logs in the Airflow UI or at least a subset of the logs generated by the callbacks.

In addition, I would like a surefire way to confirm on the Airflow UI that the scheduler sent the DagCallbackRequest and the DAGFileProcessorProcess handled the callback requqest.

### Use case/motivation

I had written a DAG with `on_success_callback` set and I noticed that certain dagruns did not generate the corresponding `on_success_callback` in the DAGFileProcessorProcess logs.

### 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)

Start by tracing how the scheduler sends the DagCallbackRequest and how the DAGFileProcessorProcess handles it, then identify where the Airflow UI exposes DagRun logs or callback status. Done should include a visible way to inspect callback logs or a defined subset and a reliable UI indication that the request was sent and handled.

Written by the indexing model from the issue text.