VITE_API_URL was /api but all API paths already included /api/,
resulting in /api/api/config etc. Config call failed silently and
defaulted to requireInvite:false. Set VITE_API_URL to empty string
so paths like /api/auth/anonymous go through nginx as-is.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>