♿️ Fix AA contrast and move mobile language selector to header row

Darken burufugu primary-600 to pass 4.5:1 on white, bump the search
shortcut hint to neutral-500, and surface the language switcher in
the visible mobile header row instead of the menu dialog.

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

layouts/partials/header/components/desktop-menu.html

@@ -37,7 +37,7 @@
       {{ partial "icon.html" "search" }}
       <kbd
         id="search-shortcut-hint"
-        class="pointer-events-none font-sans text-xs text-neutral-400 dark:text-neutral-500"
+        class="pointer-events-none font-sans text-xs text-neutral-500 dark:text-neutral-400"
         aria-hidden="true">
         ⌘K
       </kbd>