[codex] Rename strategy plugin alert settings

[Pigbibi]

Summary

• rename strategy plugin alert settings from CRISIS_ALERT to STRATEGY_PLUGIN_ALERT
• update missing-field messages and notification tests

Validation

• env PYTHONPATH=src python -m pytest -q tests/test_strategy_plugin_alert_dispatcher.py tests/test_strategy_plugin_email_notifications.py tests/test_strategy_plugin_sms_notifications.py tests/test_strategy_plugin_push_notifications.py tests/test_strategy_plugin_telegram_notifications.py