Add bounce rate to admin Analytics dashboard

Bounce rate = visitors with only 1 pageview / total visitors.
Color-coded: green <40%, yellow <60%, red >=60%.

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

src/Controller/AdminController.php

@@ -695,6 +695,18 @@ class AdminController extends AbstractController
             ->getQuery()
             ->getSingleScalarResult();
 
+        // Bounce rate: visitors with only 1 pageview
+        $bouncedVisitors = (int) $em->createQueryBuilder()
+            ->select('COUNT(v.id)')
+            ->from(AnalyticsUniqId::class, 'v')
+            ->where('v.createdAt >= :since')
+            ->andWhere('(SELECT COUNT(e2.id) FROM '.AnalyticsEvent::class.' e2 WHERE e2.visitor = v.id) = 1')
+            ->setParameter('since', $since)
+            ->getQuery()
+            ->getSingleScalarResult();
+
+        $bounceRate = $visitors > 0 ? round($bouncedVisitors / $visitors * 100, 1) : 0;
+
         $topPages = $em->createQueryBuilder()
             ->select('e.url, COUNT(e.id) AS hits')
             ->from(AnalyticsEvent::class, 'e')
@@ -755,6 +767,7 @@ class AdminController extends AbstractController
             'period' => $period,
             'visitors' => $visitors,
             'pageviews' => $pageviews,
+            'bounce_rate' => $bounceRate,
             'top_pages' => $topPages,
             'top_referrers' => $topReferrers,
             'devices' => $devices,

templates/admin/analytics.html.twig

@@ -30,8 +30,8 @@
             <p class="text-3xl font-black">{{ visitors > 0 ? (pageviews / visitors)|number_format(1) : '0' }}</p>
         </div>
         <div class="admin-card text-center">
-            <p class="text-[10px] font-black uppercase tracking-widest text-gray-400 mb-1">Periode</p>
-            <p class="text-xl font-black">{{ {today: "Aujourd'hui", '7d': '7 derniers jours', '30d': '30 derniers jours', all: 'Depuis le debut'}[period] }}</p>
+            <p class="text-[10px] font-black uppercase tracking-widest text-gray-400 mb-1">Bounce Rate</p>
+            <p class="text-3xl font-black {% if bounce_rate < 40 %}text-green-600{% elseif bounce_rate < 60 %}text-yellow-600{% else %}text-red-600{% endif %}">{{ bounce_rate }}%</p>
         </div>
     </div>