Add ability to view and manage DLC products with role-based access

Implement API endpoints for fetching DLC products, their statistics, and individual details, with filtering and permission checks based on user roles and group IDs. Update storage methods to support group-based filtering for customer orders, DLC products, and tasks.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 7c468936-2a88-4686-ac0a-84921a45222d
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/7c468936-2a88-4686-ac0a-84921a45222d/KsafRhL

client/src/pages/DlcPage.tsx

@@ -442,7 +442,7 @@ export default function DlcPage() {
     }
   };
 
-  const filteredProducts = dlcProducts.filter(product => {
+  const filteredProducts = (dlcProducts || []).filter(product => {
     if (searchTerm) {
       return product.productName.toLowerCase().includes(searchTerm.toLowerCase()) ||
              (product.supplier?.name && product.supplier.name.toLowerCase().includes(searchTerm.toLowerCase()));