Add sow-* page styles for /news /blog /gallery

The file-based pages plugin ships templates that use sow-* classes,
which had no CSS anywhere (live styles were never defined either).
Style them from DESIGN.md: velvet panels, gilt-edge borders, Cinzel
etched headings, dark-gold-plate primary buttons.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

theme.scss

@@ -10,4 +10,5 @@
 @import "./scss/westgate/search";
 @import "./scss/westgate/controls";
 @import "./scss/westgate/widgets";
+@import "./scss/westgate/pages";
 @import "./scss/westgate/responsive";