implemented basis of login, missing database connection.

app/models/user.py

@@ -0,0 +1,14 @@
+from .. import db
+from flask_login import UserMixin
+
+class User(UserMixin, db.Model):
+    __tablename__ = "users"
+
+    id = db.Column(db.Integer, primary_key=True)
+    username = db.Column(db.String(20), unique=True, nullable=False)
+    password = db.Column(db.String(255), nullable=False)  # <- größer!
+    email = db.Column(db.String(120), unique=True, nullable=False)
+    created_at = db.Column(db.DateTime, server_default=db.func.now())
+
+    def __repr__(self):
+        return f"<User {self.username}>"