refactor(tests): migrate legacy redis_client imports to autobot_shared (#2047)

[mrveiss]

Summary

• Replaces all from utils.redis_client imports in 5 backend test files with canonical from autobot_shared.redis_client
• Files changed: async_baseline.performance_test.py, redis_listeners.e2e_test.py, redis_prometheus_metrics_test.py, redis_thread_safety_test.py, redis_consolidation_test.py
• Leaves string literals in redis_optimizer_test.py untouched (they are test fixture code, not actual imports)
• Closes Tech debt: Legacy utils.redis_client imports in test files #2047

Test plan

• Verify no remaining from utils.redis_client in backend test files
• Pre-commit hooks pass (flake8, isort, black)

🤖 Generated with Claude Code

[github-actions]

✅ SSOT Configuration Compliance: Passing

🎉 No hardcoded values detected that have SSOT config equivalents!

[mrveiss]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

All 5 import migrations correctly follow CLAUDE.md Rule 2 canonical pattern (from autobot_shared.redis_client import get_redis_client). Import paths verified against autobot_shared/redis_client.py exports. No logic changes beyond import paths.

Minor observations (below reporting threshold, not blocking):

• autobot-shared/redis_client.py docstring still documents from utils.redis_client import get_redis_client as "MANDATORY USAGE PATTERN" — stale, contradicts CLAUDE.md Rule 2. Pre-existing, not introduced by this PR.
• redis_thread_safety_test.py:280 accesses redis_client_module.datetime which doesn't exist on either the old or new module — pre-existing broken test, not introduced by this PR.
• autobot_shared/redis_client.py imports from utils.redis_management.* (backend-specific) — pre-existing architectural coupling, not in scope.

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