refactor(concurrent-control): make locks redis-first

[earayu]

Scope

Task #38: concurrent_control Redis-first hardening.

• Default lock resolution now uses APERAG_LOCK_TYPE, defaulting to redis instead of threading.
• Added public create_distributed_lock(...) API for Redis-backed production locks.
• Kept threading locks as explicit opt-in for single-process/test/local usage.
• Serialized RedisLock acquire/release operations and captured owner value before async release work to fix the local _lock_value race.
• Latest main already removed old aperag/service/evaluation_service.py in cleanup(phase8/task39): legacy ORM carve + old evaluation stack hard-delete + partial unique indexes #1670/[Features] support chinese model baichuan-13b #39, so there is no remaining legacy eval bridge to update in this PR.

Gates

• uv run --extra test python -m pytest tests/unit_test/concurrent_control tests/unit_test/test_modularization_boundaries.py -q -> 110 passed, 3 warnings
• uv run ruff format --check aperag/concurrent_control tests/unit_test/concurrent_control -> pass
• uv run ruff check aperag/concurrent_control tests/unit_test/concurrent_control -> pass
• git diff --check -> pass
• rg "get_or_create_lock\\(" aperag -g '*.py' -g '!aperag/concurrent_control/manager.py' -> no production callers
• rg "lock_type=\\\"threading\\\"|\\\"threading\\\"\\)" aperag -g '*.py' -g '!aperag/concurrent_control/manager.py' -> no production callers
• rg "evaluation_service|from aperag\\.concurrent_control\\.redis_lock import RedisLock|RedisLock\\(" aperag -g '*.py' -> only concurrent_control internals