feat: enhance sales stats with device stats, per-tariff charts, and dual-series trials

- Add DualAreaChart component for two-series visualization (registrations vs trials)
- Add MultiSeriesAreaChart component for N-series tariff breakdown with dynamic pivoting
- AddonsTab: add device purchases and device revenue stat cards
- SalesTab: add per-tariff daily sales chart using MultiSeriesAreaChart
- TrialsTab: replace single-series area chart with dual-series registrations + trials chart
- Update TypeScript interfaces to match backend schema changes
- Add i18n keys for all new UI elements across en, ru, zh, fa locales

src/components/sales-stats/AddonsTab.tsx

@@ -50,7 +50,7 @@ export function AddonsTab({ params }: AddonsTabProps) {
 
   return (
     <div className="space-y-4">
-      <div className="grid grid-cols-1 gap-3 sm:grid-cols-3">
+      <div className="grid grid-cols-2 gap-3 sm:grid-cols-3 lg:grid-cols-5">
         <StatCard
           label={t('admin.salesStats.addons.totalPurchases')}
           value={data.total_purchases}
@@ -64,6 +64,15 @@ export function AddonsTab({ params }: AddonsTabProps) {
           value={formatWithCurrency(data.addon_revenue_kopeks / SALES_STATS.KOPEKS_DIVISOR)}
           valueClassName="text-success-400"
         />
+        <StatCard
+          label={t('admin.salesStats.addons.devicePurchases')}
+          value={data.device_purchases}
+        />
+        <StatCard
+          label={t('admin.salesStats.addons.deviceRevenue')}
+          value={formatWithCurrency(data.device_revenue_kopeks / SALES_STATS.KOPEKS_DIVISOR)}
+          valueClassName="text-success-400"
+        />
       </div>
 
       <div className="grid grid-cols-1 gap-4 lg:grid-cols-2">