Refactor betterPricesMap updates in RevenueSection for Vue 3 reactivity

- Updated the handling of betterPricesMap to create a new object for state updates, ensuring reactivity in Vue 3.
- This change replaces direct assignments with spread operator syntax to maintain the integrity of the reactive system.
- Aims to improve performance and align with Vue 3 best practices for state management.

frontend/src/components/falukant/RevenueSection.vue

@@ -131,11 +131,17 @@
               }
             });
             // Speichere betterPrices in einem separaten Map, nicht auf dem product Objekt
-            // In Vue 3 ist $set nicht mehr nötig, direkte Zuweisung funktioniert
-            this.betterPricesMap[product.id] = data || [];
+            // In Vue 3 müssen wir ein neues Objekt erstellen, um die Reaktivität zu triggern
+            this.betterPricesMap = {
+              ...this.betterPricesMap,
+              [product.id]: data || []
+            };
           } catch (error) {
             console.error(`Error loading prices for product ${product.id}:`, error);
-            this.betterPricesMap[product.id] = [];
+            this.betterPricesMap = {
+              ...this.betterPricesMap,
+              [product.id]: []
+            };
           } finally {
             this.loadingPrices.delete(product.id);
           }