- 7 categories now listed with name, blurb, post count and a
per-category terminal-style SVG illustration (CategoryArt)
- empty categories show '0 posts · coming soon' (non-link, no soft-404)
- new zh pages: /zh/categories/ index + /zh/categories/[category]/ detail
- PostList is locale-aware (zh-CN dates, zh category links)
- zh nav '分类' now points to /zh/categories/
- category detail pages get art + description header
- language switch wired both ways (EN <-> ZH)
