The installer was only creating base config.yaml in standalone mode,
but update_allowed_nodes() is also called in LXC mode. When the config
didn't exist, update_allowed_nodes() would create an empty file and only
add the allowed_nodes section, missing required fields like
allowed_peer_uids, metrics_address, rate_limit, etc.
This caused the proxy to fail when it tried to parse the incomplete config.
Now creates a proper base config with all required fields if the file
doesn't exist, before any mode-specific configuration is added.
49cc2927f3