hub: overview is a headerless landing with hero image
The hub overview now starts directly with the hero — no masthead/profile-header/
view-switcher/bottom-tab (those belong to a PrutFolio and appear on /user/
pages). Hero supports a background image (setting hub_hero_image, configurable
in Admin) with a dark overlay; otherwise gradient. Roster avatars use each
artist's accent color.
- shell.ejs: chrome gated on bodyClass 'on-hub'.
- hub.js: artists.accent + hub.heroImage from settings.
- admin-settings: hub_hero_image field.
Co-Authored-By: Claude <noreply@…>