pairing: LAN-IP auto-detect with localhost fallback
Teach pairing host URL resolution to prefer an explicit override, then a detected LAN IPv4 when network access is enabled, and otherwise fall back to localhost. This gives pairing and status surfaces a stable effective URL without requiring a manual host URL on the common path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>