Config parses and validates the JSON settings (D34): required device name
and broker host, defaults, type checks, device id from ha_unique_id or
derived from the name (D31), warnings for unknown keys and for a password
in a file others can read. Dashboard::prepare() loads it in overlay and
desktop mode; --config selects another file (D22). New static library
frameassistant_lib for app logic; tst_config covers it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
