The SPA doesn't send X-API-Key, so a non-empty api_key made the dashboard
401 and show no cameras. Default api_key to "" (no auth) for the closed
travel-router network, consistent with anonymous MQTT. Document the kiosk
decision, the GoPro Hero 3 protocol, and the gotcha that the pull updater
deploys only the binary (config.yaml must be changed on the Pi).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>