Add batch price retrieval for products in region

- Implemented a new endpoint to fetch prices for multiple products in a specified region in a single request, improving efficiency.
- Added validation for input parameters to ensure proper data handling.
- Updated the FalukantService to calculate prices based on knowledge factors and worth percentages for each product.
- Modified the frontend to utilize the new batch endpoint, optimizing the loading of product prices.

backend/controllers/falukantController.js

@@ -162,6 +162,18 @@ class FalukantController {
             }
             return this.service.getProductPriceInRegion(userId, productId, regionId);
         });
+        this.getProductPricesInRegionBatch = this._wrapWithUser((userId, req) => {
+            const productIds = req.query.productIds;
+            const regionId = parseInt(req.query.regionId, 10);
+            if (!productIds || Number.isNaN(regionId)) {
+                throw new Error('productIds (comma-separated) and regionId are required');
+            }
+            const productIdArray = productIds.split(',').map(id => parseInt(id.trim(), 10)).filter(id => !Number.isNaN(id));
+            if (productIdArray.length === 0) {
+                throw new Error('At least one valid productId is required');
+            }
+            return this.service.getProductPricesInRegionBatch(userId, productIdArray, regionId);
+        });
         this.getProductPricesInCities = this._wrapWithUser((userId, req) => {
             const productId = parseInt(req.query.productId, 10);
             const currentPrice = parseFloat(req.query.currentPrice);