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>

plugin.json

@@ -9,6 +9,7 @@
     { "hook": "filter:user.saveSettings", "method": "saveUserSettings" },
     { "hook": "filter:user.profileMenu", "method": "addProfileItem" },
     { "hook": "filter:middleware.renderHeader", "method": "filterMiddlewareRenderHeader" },
+    { "hook": "filter:middleware.renderFooter", "method": "filterMiddlewareRenderFooter" },
     { "hook": "filter:user.iconBackgrounds", "method": "getIconBackgrounds" }
   ],
   "scripts": ["public/client.js", "../nodebb-theme-harmony/public/harmony.js"],