Add batch processing for product price retrieval: Implement getProductPricesInCitiesBatch method in FalukantService for handling multiple product price requests in a single API call. Update FalukantController and router to support new endpoint, and refactor RevenueSection and SaleSection components to utilize batch processing for improved performance and reduced API calls.

backend/controllers/falukantController.js

@@ -214,6 +214,16 @@ class FalukantController {
             }
             return this.service.getProductPricesInCities(userId, productId, currentPrice, currentRegionId);
         });
+        this.getProductPricesInCitiesBatch = this._wrapWithUser((userId, req) => {
+            const body = req.body || {};
+            const items = Array.isArray(body.items) ? body.items : [];
+            const currentRegionId = body.currentRegionId != null ? parseInt(body.currentRegionId, 10) : null;
+            const valid = items.map(i => ({
+                productId: parseInt(i.productId, 10),
+                currentPrice: parseFloat(i.currentPrice)
+            })).filter(i => !Number.isNaN(i.productId) && !Number.isNaN(i.currentPrice));
+            return this.service.getProductPricesInCitiesBatch(userId, valid, Number.isNaN(currentRegionId) ? null : currentRegionId);
+        });
         this.renovate = this._wrapWithUser((userId, req) => this.service.renovate(userId, req.body.element));
         this.renovateAll = this._wrapWithUser((userId) => this.service.renovateAll(userId));