Add how-to for Dag-level retry via on_failure_callback

[yuseok89]

As discussed on the Airflow devlist, this PR adds documentation that addresses the short-term needs of users who want Dag-level retry behavior. The recipe combines on_failure_callback with the public REST API to clear and retry a failed Dag run.

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)
  • Opus 4.7

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