isSessionValid previously checked verifyIPSession() first, falling back to
verifySessionCookie() only if IP miss. Under Caddy --network host forward_auth,
req.ip arrived as 100.121.150.22 (DNS2 tailnet) instead of the user's real IP,
causing every cross-subdomain auto-login (plex/jellyfin/emby/chat) to 401 even
with a valid cookie. Now cookie-only; the IP cache write-back is kept as a
no-op for telemetry compat.
Verification on DNS2: /dashcaddy-login renders in 184ms (was 7s).
app-token/plex with the TOTP-issued cookie returns 200 with a real Plex token.
Krystie
96e2ef8609