Add 卓米会 mini program and admin server.

Initial commit of the WeChat mini program, Express backend, and admin console.

Co-authored-by: Cursor <cursoragent@cursor.com>

miniprogram/pages/past-edit/past-edit.wxml

@@ -0,0 +1,42 @@
+<view class="page">
+  <view class="card">
+    <text class="label">活动名称</text>
+    <input
+      class="input"
+      placeholder="例如：卓米会城市沙龙"
+      placeholder-class="placeholder"
+      value="{{title}}"
+      maxlength="40"
+      bindinput="onTitle"
+    />
+    <text class="label">活动时间</text>
+    <input
+      class="input"
+      placeholder="例如：2026-05-22 19:00"
+      placeholder-class="placeholder"
+      value="{{startAt}}"
+      maxlength="32"
+      bindinput="onTime"
+    />
+
+    <text class="label">封面图片</text>
+    <view class="media-row">
+      <image wx:if="{{cover}}" class="preview" src="{{coverPreview}}" mode="aspectFill" />
+      <view class="media-btn" bindtap="pickCover">{{cover ? '更换图片' : '选择图片'}}</view>
+      <view wx:if="{{cover}}" class="media-btn ghost" bindtap="clearCover">清除</view>
+    </view>
+
+    <text class="label">活动视频</text>
+    <view class="media-row">
+      <text class="media-name">{{video ? '已选择视频' : '未选择'}}</text>
+      <view class="media-btn" bindtap="pickVideo">{{video ? '更换视频' : '选择视频'}}</view>
+      <view wx:if="{{video}}" class="media-btn ghost" bindtap="clearVideo">清除</view>
+    </view>
+
+    <view class="pin-row" bindtap="togglePinned">
+      <view class="check {{pinned ? 'on' : ''}}"></view>
+      <text>创建后置顶（可同时置顶多个）</text>
+    </view>
+  </view>
+  <view class="save {{saving ? 'busy' : ''}}" bindtap="save">{{saving ? '保存中…' : '保存'}}</view>
+</view>