feat: 初始版本，圆角主题与首次管理员引导

app/templates/setup/admin.html

@@ -0,0 +1,13 @@
+{% extends 'base.html' %}
+{% block title %}创建管理员{% endblock %}
+{% block content %}
+<h3 class="mb-3">首次使用：创建管理员</h3>
+<form class="card p-3" method="post">
+  <input type="hidden" name="csrf_token" value="{{ csrf_token }}">
+  <div class="mb-3"><label class="form-label">邮箱</label><input class="form-control" name="email" type="email" required></div>
+  <div class="mb-3"><label class="form-label">用户名</label><input class="form-control" name="username" required></div>
+  <div class="mb-3"><label class="form-label">密码</label><input class="form-control" name="password" type="password" required></div>
+  <div class="mb-3"><label class="form-label">确认密码</label><input class="form-control" name="confirm" type="password" required></div>
+  <button class="btn btn-brand" type="submit">创建管理员</button>
+</form>
+{% endblock %}