Refactor emergency controllers to share SQLAlchemy mixin

[brothercorvo]

Summary

• add a reusable SQLAlchemyControllerMixin with session factory resolution, identifier coercion, and async CRUD helpers
• refactor the emergency example controllers to inherit from the mixin for concise method bodies
• add dedicated mixin unit tests, update example controller tests, and record the completed work in TASK.md

Testing

• ./venv_linux/bin/flake8 reticulum_openapi/sqlalchemy_controller.py examples/EmergencyManagement/Server/controllers_emergency.py tests/test_sqlalchemy_controller.py
• ./venv_linux/bin/pytest tests/test_sqlalchemy_controller.py tests/test_example_emergency_management.py::test_event_controller_list_without_session_factory tests/test_example_emergency_management.py::test_emergency_action_message_crud tests/test_example_emergency_management.py::test_event_controller_crud

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Codex Task