use aclose for arq pool shutdown

[Yashi248]

Summary

• Replaced deprecated arq_pool.close() with arq_pool.aclose() in API lifespan shutdown and worker shutdown.
• Added regression coverage asserting aclose() is awaited and close() is not called.

Verification

• uv run pytest -o cache_dir=.pytest-cache-local backend/tests/unit/test_main_lifespan.py backend/tests/unit/test_workers.py - 14 passed
• uv run ruff check backend/app/main.py backend/workers/all.py backend/tests/unit/test_main_lifespan.py backend/tests/unit/test_workers.py - passed
• rg -n "arq_pool\.close\(\)" backend/app backend/workers - no matches of deprecated calls

[gemini-code-assist]

Code Review

This pull request replaces deprecated arq_pool.close() calls with arq_pool.aclose() in both the application lifespan and worker shutdown hooks, and adds corresponding unit tests. The feedback highlights that in the new tests, asserting that close is not called is currently unreachable because calling and awaiting a non-async MagicMock would raise a TypeError first. To make these assertions robust, the reviewer suggests mocking close as an AsyncMock as well.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[SoundMindsAI]

Review adjudication — ready to merge

Replacing the deprecated arq_pool.close() with aclose() is correct: arq 0.28's ArqRedis extends redis-py 5.3.1's Redis, where close() is decorated @deprecated_function(version="5.0.1", reason="Use aclose() instead"). Both pool-shutdown sites are covered (backend/app/main.py lifespan + backend/workers/all.py on_shutdown) — no other sites missed, and the openai_client.close() calls are correctly left alone (the OpenAI SDK's close() is not deprecated).

Gemini Code Assist findings

#	File / line	Finding	Verdict	Notes
1	test_main_lifespan.py:86	close.assert_not_called() is shadowed by a TypeError in a regression scenario (awaiting a non-async MagicMock)	Accept — addressed by author	fake_pool.close now mocked as AsyncMock, so the negative assertion fails cleanly instead of crashing.
2	test_workers.py:120	Same issue in the worker-shutdown test	Accept — addressed by author	Same fix applied.

Both findings resolved by the author in 492942c. Verified locally on the updated head: 14/14 unit tests pass, ruff clean, DCO sign-off intact, single Conventional Commit.

CI

All code-validating jobs green (backend lint/typecheck/tests/coverage, frontend, docker buildx, license, DCO, secrets-defense). The smoke job is red only because forked PRs cannot access the OPENAI_API_KEY_TEST repository secret — an environmental fork limitation, not a code defect, and a non-required check. Branch was updated onto current main (30a4d0b9) before this run.

Merging.