UI: Use bulk clearDagRuns endpoint for bulk Dag run clear

[pierrejeambrun]

Wires the Dag Runs bulk-clear action to the new POST /dags/{dag_id}/clearDagRuns bulk endpoint, replacing the previous client-side fan-out that issued one single-run clear request per selected run.

• useBulkClearDagRuns now makes a single atomic clearDagRuns call (~ wildcard, each entry carries its own dag_id) instead of Promise.allSettled over per-run calls.
• useBulkClearDagRunsDryRun now makes a single dry-run call instead of a useQueries fan-out.
• BulkClearDagRunsButton is unchanged — both hooks keep their signatures and return shapes.

Behavior change: the bulk clear is now atomic — all selected runs clear or none do. The previous fan-out allowed partial success (clear the runs that succeed, report per-run errors). This aligns dag-run bulk clear with the existing post_clear_task_instances endpoint, which is already a single all-or-nothing transaction. On failure the dialog stays open and shows a single request-level error.

Depends on #67709 (the bulk endpoint + regenerated client live on that branch). This PR is stacked on it — until #67709 merges, the diff here also shows #67709's commits; the UI change itself is the single commit "UI: Use bulk clearDagRuns endpoint instead of per-run fan-out".

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

• Yes — Claude Code (Opus 4.8)

Generated-by: Claude Code (Opus 4.8) following the guidelines

[pierrejeambrun]

Screen.Recording.2026-06-02.at.15.09.56.mov

Screen.Recording.2026-06-02.at.15.12.37.mov

[pierrejeambrun]

[github-actions]

Backport failed to create: airflow-ctl/v0-1-test. View the failure log Run details

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
❌	airflow-ctl/v0-1-test

You can attempt to backport this manually by running:

cherry_picker 7651e4b airflow-ctl/v0-1-test

This should apply the commit to the airflow-ctl/v0-1-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

If you don't have cherry-picker installed, see the installation guide.