feat: 初始版本，圆角主题与首次管理员引导

app/templates/activities/list.html

@@ -0,0 +1,10 @@
+{% extends 'base.html' %}
+{% block title %}活动{% endblock %}
+{% block content %}
+<h3>活动</h3>
+<ul>
+  {% for a in activities %}
+  <li><a href="{{ url_for('activities.detail', act_id=a.id) }}">{{ a.title }}</a></li>
+  {% endfor %}
+</ul>
+{% endblock %}