Fix the slider pause label and three contrast findings in 1.12.1

Lighthouse and axe on the Elektro Bernhard site: the slider pause button
had visible text "Pause" but an accessible name that did not contain it
(WCAG 2.5.3); the name now starts with the visible text. On the site the
brand names and the footer credit link lacked contrast and the services
page jumped from H1 to H3. After the fixes: axe zero violations on six
pages, Lighthouse 100 everywhere except mobile home performance 99.
Measurements documented in docs/QUALITY.md.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

public/assets/slider.js

@@ -76,7 +76,8 @@ export function initSliders(doc = document) {
       dots.forEach((dot, i) => { dot.hidden = !visible.includes(i); dot.setAttribute('aria-pressed', String(i === index)); });
       if (play) {
         play.textContent = playing ? 'Pause' : 'Wiedergabe'; play.dataset.playing = String(playing);
-        play.setAttribute('aria-label', playing ? 'Automatische Wiedergabe pausieren' : 'Automatische Wiedergabe starten');
+        // Der zugängliche Name beginnt mit dem sichtbaren Text (WCAG 2.5.3): wer „Pause“ liest, kann „Pause“ sagen.
+        play.setAttribute('aria-label', playing ? 'Pause: automatische Wiedergabe anhalten' : 'Wiedergabe: automatisch weiterblättern');
         play.disabled = reduced(); play.title = reduced() ? 'Automatik ist bei reduzierter Bewegung deaktiviert.' : '';
       }
     };