Apply remaining audit fixes; document radii and code palette in DESIGN.md

- Token sweep: exact-value gold literals now use --wg-border /
  --wg-border-soft / --wg-focus
- Topbar: drop invalid role="menuitem" (no parent role="menu")
- topics_list: topic-select icons get role="checkbox", tabindex,
  aria-label; client.js makes them keyboard-operable and syncs
  aria-checked
- category.tpl: copy-handle link gets an accessible name, "View
  Original" moved to i18n, external-link icon aria-hidden, stretched
  link inside aria-hidden alert removed from tab order
- Footer: all copy moved to [[westgate:footer.*]] keys; year injected
  via filter:middleware.renderFooter instead of hard-coded 2026
- client.js: batch table measurements before writes (no interleaved
  reflow), .catch on the category class map so search results never
  hang, category selector match uses fw-bold class instead of inline
  style
- Forced-colors focus fallback: transparent outline alongside the
  box-shadow focus ring
- DESIGN.md: real radius scale (3/4/6/8px), code-block palette,
  motion & modes section, placeholder alpha

Verified against the sow-nodebb dev container: themed code blocks
render in posts, footer i18n + year, checkbox roles in served HTML.

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

templates/partials/category/selector-dropdown-content.tpl

@@ -24,7 +24,7 @@
         {{{ each categoryItems }}}
         <li role="presentation" class="category {{{ if ./disabledClass }}}disabled {{{ end }}}{{{ if ./class }}} {./class}{{{ end }}}" data-cid="{./cid}" data-name="{./name}" data-parent-cid="{./parentCid}">
             <a class="dropdown-item rounded-1 {{{ if ./disabledClass }}}disabled{{{ end }}}" role="menuitem" href="#">{./level}
-                <span component="category-markup" style="{{{ if ./match }}}font-weight: bold;{{{end}}}">
+                <span component="category-markup" class="{{{ if ./match }}}fw-bold{{{end}}}">
                     <span class="category-item d-inline-flex align-items-center gap-1 {{{ if ./class }}}{./class}{{{ end }}}">
                         {{{ if ./icon }}}
                         {{buildCategoryIcon(@value, "24px", "rounded-circle")}}