Celery: Ignore redelivered message for already-running task

[anishgirianish]

Catch TaskAlreadyRunningError from the supervisor and raise Celery Ignore() to prevent the broker redelivery from being recorded as a task failure.

related: #58441

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

• Yes (please specify the tool below)

Summary

Catch TaskAlreadyRunningError from the supervisor and raise Celery Ignore() to prevent a broker redelivery from being recorded as a task failure.

In Airflow 3.x, the scheduler processes executor events for RUNNING tasks (not just QUEUED as in 2.x). When Celery redelivers a message for a task that's already running, the worker hits a 409 from the API server. Without this fix, Celery records it as FAILURE, and the scheduler marks the still-running task as failed.

related: #58441
depends on: #60855

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[jscheffl]

Assume will fail unless #60855 is merged... which is fair. Can be re-based once the other PR is merged.

[potiuk]

@anishgirianish This PR has been converted to draft because it does not yet meet our Pull Request quality criteria.

Issues found:

• ❌ mypy (type checking): Failing: CI image checks / MyPy checks (mypy-providers). Run prek --stage manual mypy-providers --all-files locally to reproduce. You need breeze ci-image build --python 3.10 for Docker-based mypy. See mypy (type checking) docs.
• ❌ Provider tests: Failing: Postgres tests: providers / DB-prov:Postgres:14:3.10:-amazon,celer...standard, MySQL tests: providers / DB-prov:MySQL:8.0:3.10:-amazon,celer...standard, Sqlite tests: providers / DB-prov:Sqlite:3.10:-amazon,celer...standard, Special tests / Min SQLAlchemy test: providers / DB-prov:MinSQLAlchemy-Postgres:14:3.10:-amazon,celer...standard, Special tests / Latest SQLAlchemy test: providers / DB-prov:LatestSQLAlchemy-Postgres:14:3.10:-amazon,celer...standard (+2 more). Run provider tests with breeze run pytest <provider-test-path> -xvs. See Provider tests docs.

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[jscheffl]

@potiuk This is an exception where your AI tooling is not right - all the errors are caused by the explicit split PR #60855 not being merged (yet). Once this is done a rebase most probably will fix all errors. Re-converted to "Ready for review".