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/topics_list.tpl

@@ -15,7 +15,7 @@
 				</a>
 				{{{ if showSelect }}}
 				<div class="checkbox position-absolute top-100 start-50 translate-middle-x pt-2 m-0 d-none d-lg-flex" style="max-width:max-content">
-					<i component="topic/select" class="fa text-muted pointer fa-square-o p-1 hover-visible"></i>
+					<i component="topic/select" class="fa text-muted pointer fa-square-o p-1 hover-visible" role="checkbox" aria-checked="false" tabindex="0" aria-label="[[westgate:select-topic]]"></i>
 				</div>
 				{{{ end }}}
 			</div>
@@ -73,7 +73,7 @@
 				</span>
 				{{{ if showSelect }}}
 				<div class="checkbox position-absolute top-0 end-0 m-0 d-flex d-lg-none" style="max-width:max-content">
-					<i component="topic/select" class="fa fa-square-o text-muted pointer p-1"></i>
+					<i component="topic/select" class="fa fa-square-o text-muted pointer p-1" role="checkbox" aria-checked="false" tabindex="0" aria-label="[[westgate:select-topic]]"></i>
 				</div>
 				{{{ end }}}
 			</div>