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.

frontend/src/views/falukant/BranchView.vue

@@ -572,27 +572,49 @@ export default {
                 return;
             }
             
-            // Lade Preise für alle Produkte in der aktuellen Region
-            const prices = {};
-            for (const product of this.products) {
-                try {
-                    const { data } = await apiClient.get('/api/falukant/products/price-in-region', {
-                        params: {
-                            productId: product.id,
-                            regionId: this.selectedBranch.regionId
-                        }
-                    });
-                    prices[product.id] = data.price;
-                } catch (error) {
-                    console.error(`Error loading price for product ${product.id}:`, error);
-                    // Fallback auf Standard-Berechnung
-                    const knowledgeFactor = product.knowledges?.[0]?.knowledge || 0;
-                    const maxPrice = product.sellCost;
-                    const minPrice = maxPrice * 0.6;
-                    prices[product.id] = minPrice + (maxPrice - minPrice) * (knowledgeFactor / 100);
-                }
+            if (!this.products || this.products.length === 0) {
+                this.productPricesCache = {};
+                return;
+            }
+            
+            // OPTIMIERUNG: Lade alle Preise in einem Batch-Request
+            try {
+                const productIds = this.products.map(p => p.id).join(',');
+                const { data } = await apiClient.get('/api/falukant/products/prices-in-region-batch', {
+                    params: {
+                        productIds: productIds,
+                        regionId: this.selectedBranch.regionId
+                    }
+                });
+                this.productPricesCache = data || {};
+            } catch (error) {
+                console.error('Error loading prices in batch:', error);
+                // Fallback: Lade Preise einzeln (aber parallel)
+                const pricePromises = this.products.map(async (product) => {
+                    try {
+                        const { data } = await apiClient.get('/api/falukant/products/price-in-region', {
+                            params: {
+                                productId: product.id,
+                                regionId: this.selectedBranch.regionId
+                            }
+                        });
+                        return { productId: product.id, price: data.price };
+                    } catch (err) {
+                        console.error(`Error loading price for product ${product.id}:`, err);
+                        // Fallback auf Standard-Berechnung
+                        const knowledgeFactor = product.knowledges?.[0]?.knowledge || 0;
+                        const maxPrice = product.sellCost;
+                        const minPrice = maxPrice * 0.6;
+                        return { productId: product.id, price: minPrice + (maxPrice - minPrice) * (knowledgeFactor / 100) };
+                    }
+                });
+                
+                const results = await Promise.all(pricePromises);
+                this.productPricesCache = {};
+                results.forEach(({ productId, price }) => {
+                    this.productPricesCache[productId] = price;
+                });
             }
-            this.productPricesCache = prices;
         },
 
         formatPercent(value) {