Improve Home Page admin — add Gallery Section shortcut + help note

- Expanded quick-links from 4 to 6 cards (Hero, Side Banners, Gallery,
  Bottom Banners, Products, Categories) each with position tag label
- Added direct links with ?position= filter so clicking opens Banners
  page pre-filtered to the right position
- Added step-by-step info alert explaining how to edit the gallery section

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
