Add product price retrieval feature in cities

- Implemented a new endpoint in FalukantController to fetch product prices in various cities based on product ID and current price.
- Developed the corresponding service method in FalukantService to calculate and return prices, considering user knowledge and city branches.
- Updated frontend components (RevenueSection and SaleSection) to display better prices for products, including loading logic and UI enhancements for price visibility.
- Added styling for price indicators based on branch types to improve user experience.

backend/controllers/falukantController.js

@@ -144,6 +144,14 @@ class FalukantController {
         this.applyForElections = this._wrapWithUser((userId, req) => this.service.applyForElections(userId, req.body.electionIds));
 
         this.getRegions = this._wrapWithUser((userId) => this.service.getRegions(userId));
+        this.getProductPricesInCities = this._wrapWithUser((userId, req) => {
+            const productId = parseInt(req.query.productId, 10);
+            const currentPrice = parseFloat(req.query.currentPrice);
+            if (Number.isNaN(productId) || Number.isNaN(currentPrice)) {
+                throw new Error('productId and currentPrice are required');
+            }
+            return this.service.getProductPricesInCities(userId, productId, currentPrice);
+        });
         this.renovate = this._wrapWithUser((userId, req) => this.service.renovate(userId, req.body.element));
         this.renovateAll = this._wrapWithUser((userId) => this.service.renovateAll(userId));