Fix LXMF config path handling

[brothercorvo]

Summary

• normalise the LXMF client configuration path to a usable Reticulum directory before instantiating the stack
• ensure the LXMF client prepares its storage directory prior to creating the router
• add regression coverage asserting the client normalises config files, storage overrides, and identity loads

Testing

• black reticulum_openapi/client.py tests/test_client_extra.py
• flake8 --exclude=.git,pycache,build,dist,venv_linux
• pytest tests/test_client.py tests/test_client_extra.py tests/examples/emergency_management/test_client_emergency.py

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https://chatgpt.com/codex/tasks/task_e_68d59fbad8e48325bbe994cd50f480e5