Add charts and bounce rate to admin Analytics, filter self-referrers

- Bar chart: visitors per day
- Line chart: pageviews per day (with fill)
- Bounce rate KPI with color coding (green/yellow/red)
- Filter out self-referrers (ticket.e-cosplay.fr, esyweb.local)
- Uses Chart.js via cdn.jsdelivr.net (already in CSP)

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

templates/admin/analytics.html.twig

@@ -35,6 +35,18 @@
         </div>
     </div>
 
+    {# Charts #}
+    <div class="grid grid-cols-1 lg:grid-cols-2 gap-6 mb-8">
+        <div class="admin-card">
+            <h2 class="text-sm font-black uppercase tracking-widest mb-4">Visiteurs par jour</h2>
+            <canvas id="chart-visitors" height="200"></canvas>
+        </div>
+        <div class="admin-card">
+            <h2 class="text-sm font-black uppercase tracking-widest mb-4">Pages vues par jour</h2>
+            <canvas id="chart-pageviews" height="200"></canvas>
+        </div>
+    </div>
+
     <div class="grid grid-cols-1 lg:grid-cols-2 gap-6 mb-8">
         {# Top pages #}
         <div class="admin-card">
@@ -121,4 +133,30 @@
             {% endfor %}
         </div>
     </div>
+
+    <script src="https://cdn.jsdelivr.net/npm/chart.js@4/dist/chart.umd.min.js"></script>
+    <script>
+    (function() {
+        const labels = {{ chart_labels|json_encode|raw }};
+        const opts = {
+            responsive: true,
+            maintainAspectRatio: false,
+            plugins: { legend: { display: false } },
+            scales: {
+                x: { grid: { display: false }, ticks: { font: { weight: 'bold', size: 10 } } },
+                y: { beginAtZero: true, ticks: { font: { weight: 'bold', size: 10 } } }
+            }
+        };
+        new Chart(document.getElementById('chart-visitors'), {
+            type: 'bar',
+            data: { labels, datasets: [{ data: {{ chart_visitors|json_encode|raw }}, backgroundColor: '#fabf04', borderColor: '#111827', borderWidth: 2 }] },
+            options: opts
+        });
+        new Chart(document.getElementById('chart-pageviews'), {
+            type: 'line',
+            data: { labels, datasets: [{ data: {{ chart_pageviews|json_encode|raw }}, borderColor: '#111827', backgroundColor: 'rgba(250,191,4,0.2)', borderWidth: 3, fill: true, tension: 0.3, pointBackgroundColor: '#fabf04', pointBorderColor: '#111827', pointBorderWidth: 2 }] },
+            options: opts
+        });
+    })();
+    </script>
 {% endblock %}