Fix: Apply DAG permission filter to dashboard (closes #53938)

[suhail-zemoso]

✅ Fix: Apply DAG permission filter to /dag_stats and /historical_metrics_data endpoint

📌 Closes: #53938

🔍 Summary
This PR addresses a security/visibility issue where the /dag_stats and /historical_metrics_data endpoints returned data for all DAGs, even if the requesting user lacked the necessary permissions.

To resolve this, DAG-level permission checks are now enforced using ReadableDagsFilterDep.

🛠️ What was changed
✅ Added readable_dags_filter: ReadableDagsFilterDep as a dependency to:

1. /dag_stats (returns count of DAGs in various states)
2. /historical_metrics_data (returns historical task run data)

✅ Ensured that only data from DAGs the current user has access to is included in the response

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[boring-cyborg]

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[boring-cyborg]

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[github-actions]

Backport successfully created: v3-0-test

Status	Branch	Result
✅	v3-0-test