Add product price history model and database schema: Implement associations for ProductPriceHistory with ProductType and RegionData. Update FalukantService to utilize active character for user-related operations. Ensure product price history table exists in the database with appropriate structure and indexing.

backend/models/falukant/log/product_price_history.js

@@ -0,0 +1,44 @@
+import { Model, DataTypes } from 'sequelize';
+import { sequelize } from '../../../utils/sequelize.js';
+
+/**
+ * Preishistorie pro Produkt und Region (Zeitreihe für Preis-Graphen).
+ * Aktuell wird diese Tabelle noch nicht befüllt; sie dient nur als Grundlage.
+ */
+class ProductPriceHistory extends Model { }
+
+ProductPriceHistory.init({
+    productId: {
+        type: DataTypes.INTEGER,
+        allowNull: false
+    },
+    regionId: {
+        type: DataTypes.INTEGER,
+        allowNull: false
+    },
+    price: {
+        type: DataTypes.DECIMAL(12, 2),
+        allowNull: false
+    },
+    recordedAt: {
+        type: DataTypes.DATE,
+        allowNull: false,
+        defaultValue: sequelize.literal('CURRENT_TIMESTAMP')
+    }
+}, {
+    sequelize,
+    modelName: 'ProductPriceHistory',
+    tableName: 'product_price_history',
+    schema: 'falukant_log',
+    timestamps: false,
+    underscored: true,
+    indexes: [
+        {
+            name: 'product_price_history_product_region_recorded_idx',
+            fields: ['product_id', 'region_id', 'recorded_at']
+        }
+    ]
+});
+
+export default ProductPriceHistory;
+