feat: add landing page statistics page with recharts

Add AdminLandingStats page with:
- Summary cards (purchases, revenue, gifts, conversion)
- AreaChart with dual Y-axis (daily purchases + revenue)
- BarChart (tariff distribution)
- PieChart donut (gift vs regular breakdown)
- Responsive layout for desktop and mobile
- Stats button on landing cards list

Includes API types, route, translations (ru/en).

src/App.tsx

@@ -110,6 +110,7 @@ const AdminPolicyEdit = lazy(() => import('./pages/AdminPolicyEdit'));
 const AdminAuditLog = lazy(() => import('./pages/AdminAuditLog'));
 const AdminLandings = lazy(() => import('./pages/AdminLandings'));
 const AdminLandingEditor = lazy(() => import('./pages/AdminLandingEditor'));
+const AdminLandingStats = lazy(() => import('./pages/AdminLandingStats'));
 
 function ProtectedRoute({ children }: { children: React.ReactNode }) {
   const isAuthenticated = useAuthStore((state) => state.isAuthenticated);
@@ -542,6 +543,16 @@ function App() {
             </PermissionRoute>
           }
         />
+        <Route
+          path="/admin/landings/:id/stats"
+          element={
+            <PermissionRoute permission="landings:read">
+              <LazyPage>
+                <AdminLandingStats />
+              </LazyPage>
+            </PermissionRoute>
+          }
+        />
         <Route
           path="/admin/servers"
           element={