Fix timeout_with_traceback crashes on Windows and non-main threads

[Gautam-Bharadwaj]

The timeout_with_traceback context manager in airflow.utils.db uses signal.SIGALRM to raise a TimeoutException.

However, signal.SIGALRM does not exist on Windows, causing an AttributeError. Furthermore, even on Unix, signal.signal() can only be called from the main thread, raising a ValueError inside worker threads. This completely breaks logic wrapped in this context in non-standard environments.

I have added safe exception handling around the signal initialization. If signal.SIGALRM fails due to OS constraints or thread context, it logs a warning and proceeds gracefully as a no-op timeout, instead of crashing the process.

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[potiuk]

@Gautam-Bharadwaj This PR has a few issues that need to be addressed before it can be reviewed — please see our Pull Request quality criteria.

Issues found:

• ❌ Testing Requirements: This is a bug-fix PR with no regression tests added. The checklist requires a test that fails without the fix and passes with it. The fix handles two distinct scenarios — signal.SIGALRM missing on Windows (AttributeError) and signal.signal() called from a non-main thread (ValueError) — yet neither scenario has a corresponding test. Without tests, the fix cannot be verified and could silently regress. At minimum, a parametrized test that patches signal.signal to raise AttributeError and ValueError respectively, verifying the context manager does not raise and logs a warning, is needed.

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There is no rush — take your time and work at your own pace. We appreciate your contribution and are happy to wait for updates. If you have questions, feel free to ask on the Airflow Slack.

[Gautam-Bharadwaj]

@potiuk Thanks for the review Jarek! I've rebased the branch and added comprehensive unit tests for timeout_with_traceback in airflow-core/tests/unit/utils/test_timeout_traceback.py. The tests cover:

• Normal behavior on Unix/Linux systems with SIGALRM.
• Graceful handling of AttributeError (case when SIGALRM is missing on Windows).
• Graceful handling of ValueError (case when called from a non-main thread).
• Verified that a warning is logged when timeout is unsupported.
• Verified that TimeoutException is correctly raised when the handler is triggered.
  Ready for review! 👋

[Gautam-Bharadwaj]

Hi @potiuk Sir,

Could you please take a look at this PR? If it looks good to you, please feel free to merge it.

Thanks in advance!