Isolated CalDAV transport module that reuses the browser's Nextcloud
session (cookies, no stored password). Returns a discriminated result
and detects the HTTP-200 login-page redirect by sniffing the body for
BEGIN:VCALENDAR. compterEvenements counts real VEVENT line starts as the
T1 proof of life.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
