templates/register.html

{% extends 'base.html' %}
{% block content %}
<div class="row justify-content-center">
  <div class="col-md-6">
    <div class="card shadow">
      <div class="card-body p-5">
        <h2 class="card-title text-center mb-4">Register</h2>
        <form method="post">
          <div class="mb-3">
            <label for="username" class="form-label">Username</label>
            <input type="text" class="form-control" id="username" name="username" required>
          </div>
          <div class="mb-3">
            <label for="password" class="form-label">Password</label>
            <input type="password" class="form-control" id="password" name="password" required>
          </div>
          <button type="submit" class="btn btn-primary w-100">Register</button>
        </form>
        <p class="mt-3 text-center">
          Already have an account? <a href="{{ url_for('login') }}">Login</a>
        </p>
      </div>
    </div>
  </div>
</div>
{% endblock %}