Kiosk now exposes :18090 with two surfaces:
- GET /local/layout/:id?key=<kiosk_local_key>
Bookmark-friendly layout switch on this kiosk. Auth = kiosk-generated
local key (32 random bytes, hex, stored at <state_dir>/local.key).
- ANY /proxy/* — forwards to BF server with the request's Authorization
header preserved. Lets LAN clients reach a cloud-hosted BF server via
the kiosk's local socket; kiosk adds no auth of its own.
Heartbeat reports {local_key, local_port}; kiosks table grows
local_key/local_port/local_last_ip columns. Admin kiosk edit page now
shows the local URLs as a copy-paste block.
Override port: BF_KIOSK_LOCAL_PORT. Disable: BF_KIOSK_LOCAL_DISABLE=1.
