feat(css): co-locate block CSS with auto-discovery via Tailwind pipeline

Move block-specific CSS from centralized assets/css/blox/ to co-located
style.css files within each block directory. The css.html partial now
auto-discovers style.css files from bundled and community blocks and
concatenates them into the Tailwind entry via resources.Concat, enabling
full @apply support while avoiding VFS path resolution issues.

Shared biography styles (avatar, ruby) are extracted to blox/shared/css/
and auto-included before per-block styles. Navbar CSS moves to
components/ as it's a framework-level concern. The separate community
CSS pipeline in site_head.html is removed — all block CSS now flows
through a single Tailwind entry point.

modules/blox/assets/css/components/all.css

@@ -10,3 +10,4 @@
 @import "author-notes.css";
 @import "glassmorphism.css";
 @import "cover.css";
+@import "navbar.css";