feat: enhance category breakdown and pie chart components with icon support and improved tooltip formatting

app/statistics/page.tsx

@@ -97,6 +97,7 @@ export default function StatisticsPage() {
           name: category?.name || "Non catégorisé",
           value: Math.round(total),
           color: category?.color || "#94a3b8",
+          icon: category?.icon || "HelpCircle",
         };
       })
       .sort((a, b) => b.value - a.value)