fix(pool): synchronize teardown lease releases

[axisrow]

Summary

• Route remove_client teardown cleanup through _lease_pool.release(phone) while holding ClientPool._lock.
• Route disconnect_all timeout force-cleanup through _lease_pool.release(phone) while holding ClientPool._lock.
• Route _acquire_from_lease non-shared failure cleanup through _lease_pool.release(phone) while holding ClientPool._lock.
• Add regression tests that spy on _lease_pool.release and assert ClientPool._lock is held at the release/discard point.

Validation

• pytest tests/test_client_pool_lifecycle.py -v passed.
• Mutation check: temporarily restored the old teardown/release behavior; the three new fix(pool): bare _in_use.discard вне AccountLeasePool._lock в remove_client/disconnect_all (тот же класс что #1181, teardown-пути) #1191 regression tests failed, then passed again after restoring the fix.
• pytest tests/test_main_client_pool_collector_paths.py::TestClientPoolProperties::test_remove_client -v passed.
• ruff check src/ tests/ conftest.py passed.
• pytest tests/ -v -m aiosqlite_serial passed: 941 passed, 9242 deselected.
• pytest tests/ -v -m "not aiosqlite_serial" -n auto was run after the main fix. It exposed one local test-double update, now fixed and verified, plus unrelated provider/env failures in tests/test_quality_scoring_service.py and tests/test_pipelines.py caused by live/default provider behavior and unclosed socket warnings in this environment.

Closes #1191