UI E2E test || DAG-012: Create backfill with all reprocess behaviour

[vatsrahul1001]

Description

Add E2E tests to verify the backfill creation functionality on the DAG detail page (/dags/:dagId).

What to test

• Navigate to a DAG's Backfills tab
• Open create backfill dialog/form
• Verify date range selection (start date, end date)
• Create backfill with "reprocess all" behavior
• Create backfill with "reprocess failed" behavior
• Create backfill with "reprocess none" behavior
• Verify backfill appears in list after creation
• Verify backfill status shows as running/queued
• Verify validation errors for invali

Related issues

#59028

Are you willing to submit a PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[iharsh02]

I would love to work on this issue.

[potiuk]

Feel free.

[ShivamSaurabh10]

I am Eager And Curious To Work On The Project.

[vatsrahul1001]

@ShivamSaurabh10 there are a few unassigned sub-issues under the meta issue #59028
. If you’d like to work on any of them, please comment on the unassigned issue and I’ll assign it to you.