feat(frontend): visual QA pass — unified page titles, CTAs, native controls, 404 fixes

- add PageTitle and apply it on /download, /themes, /configs, /showcase, /link, 404
- reset range-slider thumbs in the theme editor; fold color picker into the swatch
- hide horizontal scrollbars in the ClickGui mock; clip html to kill 100vw pan
- pin the footer under short pages via flex AppShell; split 404 art from caption
- one landing CTA geometry (lv-cta-lg / quiet); CLOUD eyebrow; auth caption scrim
- showcase error hides sort/pager; query retry limited to 1

frontend/src/pages/app/ConfigsPage.tsx

@@ -2,6 +2,7 @@ import { useTranslation } from 'react-i18next'
 import { ParticleField } from '../../features/landing/effects/ParticleField'
 import { VoxelScene } from '../../features/landing/effects/VoxelScene'
 import { SlotGrid } from '../../features/configs/components/SlotGrid'
+import { PageTitle } from '../../shared/ui/PageTitle'
 
 const ACCENT = 'rgb(92, 200, 231)'
 
@@ -16,13 +17,16 @@ export default function ConfigsPage() {
       <ParticleField color={ACCENT} className="opacity-50" />
 
       <div className="relative mx-auto flex w-full max-w-[1120px] flex-col gap-8 px-4 pt-12 sm:px-6">
-        <div>
-          <h1 className="font-display text-3xl text-snow">{t('page.title')}</h1>
-          <p className="mt-2 max-w-[60ch] text-frost">
-            {t('page.leadBefore')} <code className="font-code text-ice">%config save &lt;слот&gt;</code>
-            {t('page.leadAfter')}
-          </p>
-        </div>
+        <PageTitle
+          lead={
+            <>
+              {t('page.leadBefore')} <code className="font-code text-ice">%config save &lt;слот&gt;</code>
+              {t('page.leadAfter')}
+            </>
+          }
+        >
+          {t('page.title')}
+        </PageTitle>
         <SlotGrid />
       </div>
     </section>