The Site Auditor moved to the new AI Marketplace hub at
marketplace.quantumtaskai.com. Update all outbound links across the
static site so visitors land on the hub instead of going through the
audit.* 301 redirect.
Also adds the Marketplace nav entry to shared-header.js (already
present locally, now reaffirmed alongside the link updates).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>