Theme post code blocks + a11y fixes (impeccable audit) (#25)

Code blocks in posts rendered with the markdown plugin's default light highlight.js theme — white blocks on the dark ledger. This adds dark velvet pre/code styling and a Westgate-toned syntax palette (gold keywords, ledger-ink titles, muted green strings) for post content and the composer preview.

Also picks up the quick wins from an impeccable audit:

- Visible focus ring on the mobile drawer search (input had `outline: 0` with no replacement)
- Input placeholder contrast raised to pass WCAG 4.5:1; tagsinput placeholder reuses the token instead of `$gray-500`
- `prefers-reduced-motion` block zeroing transitions/animations (there were none before)
- Fixed a stray `</li>` closing a `<div>` in `quick-search-results.tpl`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #25
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

scss/westgate/_topbar.scss

@@ -189,7 +189,7 @@ $wg-topbar-panel-bg: rgba(21, 17, 26, 0.98);
 .wg-topbar .btn.btn-light:hover,
 .wg-topbar .btn.btn-light:focus {
   color: var(--wg-text) !important;
-  background: rgba(194, 163, 90, 0.08) !important;
+  background: var(--wg-border-soft) !important;
 }
 
 // one primary vocabulary: the dark gold plate from _controls.scss
@@ -296,6 +296,12 @@ $wg-topbar-panel-bg: rgba(21, 17, 26, 0.98);
   outline: 0;
 }
 
+// The input's own outline is off; put the visible focus ring on its wrapper.
+.wg-topbar__drawer-search:focus-within {
+  border-color: rgba(194, 163, 90, 0.5);
+  box-shadow: 0 0 0 1px var(--wg-focus);
+}
+
 .wg-topbar__drawer-nav,
 .wg-topbar__drawer-actions,
 .wg-topbar__drawer-auth {
@@ -323,7 +329,7 @@ $wg-topbar-panel-bg: rgba(21, 17, 26, 0.98);
 .wg-topbar__drawer-actions a:focus {
   color: var(--wg-text);
   border-color: rgba(194, 163, 90, 0.22);
-  background: rgba(194, 163, 90, 0.08);
+  background: var(--wg-border-soft);
 }
 
 @media (max-width: 1199.98px) {