Fix DAGs list page Last Run/Next Run going stale after runs complete

[bramhanandlingala]

Summary
The DAGs list page (/dags) stops auto-refreshing once none of the visible
DAGs has a run in a pending state. Since that's the normal resting
condition, "Last Run" and "Next Run" (and the Recent Tasks counts) go stale
and never update again until a manual page reload.

Root cause
useDags and useDagRunStateCounts each set refetchInterval: false
whenever no DAG on the current page is mid-run, permanently killing
polling. Every other page in the UI instead uses
useAutoRefresh({ checkPendingRuns: true }), which checks pending runs
globally and scales the interval back instead of disabling it.

Fix
Route both hooks through the same checkPendingRuns: true mechanism
already used elsewhere, instead of their own divergent, page-local gate.
No visual/markup changes — purely a polling-behavior fix.

closes: #70663

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

• Yes - Claude

Generated-by: Claude following the guidelines