Murfey server still looks for security configuration file path from environment variable instead of machine configuration

When running `murfey.server`, it appears to not get the path to the security configuration from the machine configuration, even though a key for it has already been implemented. User authentication on the FastAPI web page fails when the security configuration environment variable is unset.

Start by tracing the murfey.server startup path and the existing machine-configuration key for the security configuration path. Compare that lookup with the environment-variable handling, then verify that authentication on the FastAPI page works when the environment variable is unset.

索引モデルが issue の本文から書いたものです。