app/frontend/templates/components/sidebar.html

<div class="sidebar">
    <div class="d-flex justify-content-between align-items-center p-3">
        <form action="/new_chat" method="post">
            <button type="submit" class="btn btn-success w-100">+ Add new chat</button>
        </form>
    </div>

    {% if context.chat_groups %}
        {% for group in context.chat_groups %}
            <div class="chat-group px-3 text mt-3">{{ group.title }}</div>
            {% for chat in group.chats %}
                <form action="/chats/id={{ chat.id }}" method="get" class="px-3 my-1">
                    {% if context.selected == chat.id %}
                        <button type="submit" class="btn btn-outline-secondary w-100 text-start text-truncate text-success">
                            {{ chat.title }}
                        </button>
                    {% else %}
                        <button type="submit" class="btn btn-outline-secondary w-100 text-start text-truncate text-white">
                            {{ chat.title }}
                        </button>
                    {% endif %}
                </form>
            {% endfor %}
        {% endfor %}
    {% endif %}
</div>