style: use deep black glass morphism for content detail modal

Replace the flat #141414 grey background with a dark glass container
matching the header's floating-glass style — rgba(6,6,6,0.92) with
backdrop-filter blur, subtle white/6% border, and layered shadows.
Updated the hero gradient to blend seamlessly into the new base.

Co-authored-by: Cursor <cursoragent@cursor.com>

docker-compose.yml

@@ -20,7 +20,7 @@ services:
       context: .
       dockerfile: Dockerfile
       args:
-        CACHEBUST: "20"
+        CACHEBUST: "21"
         VITE_USE_MOCK_DATA: "false"
         VITE_CONTENT_ORIGIN: ${FRONTEND_URL}
         VITE_INDEEHUB_API_URL: /api