templates/base.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="static/css/styles.css">
    <title>Restaurant App</title>
</head>
<body>
    <div id="app">
        {{ content }}
    </div>
</body>
</html>