One category per post, display in grid without tag

Import script now takes only the first CSV category per post.
All card grid templates simplified to show just that single
category in card__sub — no tag alongside it.

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

content/posts/leather-goddess-city-twilight/index.md

@@ -9,7 +9,6 @@ image: "leather-goddess-city-twilight.png"
 weight: 47
 categories:
   - "Urban"
-  - "Noir"
 tags:
   - "Leather"
   - "Gloves"