Fix Celery worker crash on macOS due to unpicklable local function

[Vamsi-klu]

Summary

• Move bundle_cleanup_main() from a local function inside _run_stale_bundle_cleanup() to module-level _bundle_cleanup_main(check_interval)
• On macOS, multiprocessing uses spawn instead of fork, and local functions cannot be pickled for spawning across processes
• Follows the existing pattern of serve_logs (module-level function used with Process(target=serve_logs))

Co-contributors : @codingrealitylabs @girlcoder-gaming

Test plan

• Verify Celery worker starts without error on macOS
• Verify stale bundle cleanup process spawns correctly
• Run on both macOS (spawn) and Linux (fork) to confirm compatibility

Closes: #62512

🤖 Generated with Claude Code

[Vamsi-klu]

cc @vincbeck @o-nikolas @potiuk — Would appreciate your review. This fixes a Celery worker crash on macOS where spawn multiprocessing can't pickle a local function used as a Process target.

[dheerajturaga]

LGTM

[o-nikolas]

Code looks reasonable to me. Any way we can add a test to avoid future regression?

[Vamsi-klu]

Code looks reasonable to me. Any way we can add a test to avoid future regression?

@o-nikolas I have added the test for that, regression. Could you please give me feedback for the test that I have added? If everything looks good to you, could you please give me a stamp for my PR? Thank you.

[Vamsi-klu]

@codex could you give the detailed review feedback for this PR?

[bluczko]

I made the exact same change a few days ago: #62528 . What a coincidence.

[dheerajturaga]

Thanks! For catching this 😃

[potiuk]

Nice!