Implement JWT authentication and user token management

backend/models/UserToken.js

@@ -0,0 +1,20 @@
+import { DataTypes } from 'sequelize';
+import sequelize from '../database.js'; // Korrigierter Pfad
+
+const UserToken = sequelize.define('UserToken', {
+  userId: {
+    type: DataTypes.INTEGER,
+    allowNull: false,
+  },
+  token: {
+    type: DataTypes.STRING,
+    allowNull: false,
+    unique: true,
+  },
+  expiresAt: {
+    type: DataTypes.DATE,
+    allowNull: false,
+  },
+});
+
+export default UserToken;