Remove stale siren off-listener handles on retrigger

[dmulcahey]

This pull request addresses an issue with the siren entity's timed activation logic, specifically preventing the accumulation of stale canceled handles when the siren is repeatedly turned on with a timer. The changes ensure that canceled listeners are properly removed from the entity's internal tracking, preventing unbounded growth and potential resource leaks. A new test is also added to validate this behavior.

Bug fix: Proper cleanup of stale handles on repeated timed activation

• Updated the async_turn_on method in zha/application/platforms/siren.py to remove canceled listeners from the _tracked_handles set, ensuring that only active handles are tracked and preventing memory/resource leaks.

Testing improvements

• Added a new test test_siren_repeated_timed_turn_on_leaks_stale_tracked_handles in tests/test_siren.py to verify that repeated timed activations do not retain stale or canceled handles, and that the cleanup logic works as intended.## Summary
  Removes stale canceled timer handles when re-triggering timed siren activation.

Failing tests addressed

• tests/test_siren.py::test_siren_repeated_timed_turn_on_leaks_stale_tracked_handles

Verification

• pytest (branch-local targeted run): listed test passes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.51%. Comparing base (9d03d63) to head (896e40e).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #694   +/-   ##
=======================================
  Coverage   97.51%   97.51%           
=======================================
  Files          62       62           
  Lines       10949    10952    +3     
=======================================
+ Hits        10677    10680    +3     
  Misses        272      272           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.