feat: Stats-Bar ueber Karussell, Pfeil-Navigation, Count-Up

- Stats (Artikel/Quellen/Faktenchecks) als prominente Bar ueber dem
  Karussell mit Count-Up-Animation und gruener Live-Pulse-Anzeige
- Pfeil-Buttons links/rechts fuer Karussell-Navigation
- Text-Card breiter (860px)
- Stats nicht mehr in der Card

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vorschau/js/app.js

@@ -102,6 +102,16 @@
 
     positionCards(0);
 
+    // Arrow navigation
+    var prevBtn = document.querySelector('.carousel-prev');
+    var nextBtn = document.querySelector('.carousel-next');
+    if (prevBtn) prevBtn.addEventListener('click', function () {
+        positionCards((activeIndex - 1 + cards.length) % cards.length);
+    });
+    if (nextBtn) nextBtn.addEventListener('click', function () {
+        positionCards((activeIndex + 1) % cards.length);
+    });
+
     /* ==================== SIMPLE MARKDOWN ==================== */
     function mdToHtml(md) {
         if (!md) return '';
@@ -140,9 +150,23 @@
                 var es = document.getElementById('stat-sources');
                 var ef = document.getElementById('stat-factchecks');
                 var eu = document.getElementById('demo-updated');
-                if (ea) ea.textContent = inc.article_count || 0;
-                if (es) es.textContent = inc.source_count || 0;
-                if (ef) ef.textContent = inc.factcheck_count || 0;
+                function countUp(el, target) {
+                    if (!el || !target) return;
+                    var start = 0;
+                    var duration = 1200;
+                    var startTime = null;
+                    function step(ts) {
+                        if (!startTime) startTime = ts;
+                        var progress = Math.min((ts - startTime) / duration, 1);
+                        var ease = 1 - Math.pow(1 - progress, 3);
+                        el.textContent = Math.floor(ease * target).toLocaleString('de-DE');
+                        if (progress < 1) requestAnimationFrame(step);
+                    }
+                    requestAnimationFrame(step);
+                }
+                countUp(ea, inc.article_count);
+                countUp(es, inc.source_count);
+                countUp(ef, inc.factcheck_count);
                 if (eu && data.updated_at) eu.textContent = timeAgo(data.updated_at);
 
                 // Excerpt: pre-extracted in summary.json