feat: rebuild pet app and backend around core care flows

pets-fe/pages/meetups/meetups.wxml

@@ -0,0 +1,62 @@
+<view class="screen">
+  <view class="eyebrow">LET'S WALK TOGETHER</view>
+  <view class="title">约个伴一起遛 🌿</view>
+  <view class="banner">
+    <text>好天气，和新朋友一起走走</text>
+    <strong>
+      下一次快乐
+      <br />
+      从这里出发
+    </strong>
+    <image src="/assets/corgi-family-five.png" mode="aspectFit" />
+  </view>
+  <view class="row">
+    <text class="section-title">附近的约遛</text>
+    <text class="add" bindtap="create">＋ 发起约遛</text>
+  </view>
+  <view
+    wx:for="{{meetups}}"
+    wx:key="id"
+    class="card meetup"
+    data-index="{{index}}"
+    bindtap="open"
+  >
+    <view class="row">
+      <text class="badge">
+        🐾 {{item.participants}} / {{item.max_people}} 人
+      </text>
+      <text class="arrow">›</text>
+    </view>
+    <strong>{{item.title}}</strong>
+    <view class="meta">📍 {{item.place_name}}</view>
+    <view class="meta">🗓 {{item.date}}</view>
+    <view class="desc">{{item.description}}</view>
+  </view>
+  <view wx:if="{{!meetups.length}}" class="empty">
+    还没有约遛，发起第一场吧 🐕
+  </view>
+  <button class="primary" bindtap="create">＋ 发起一场约遛</button>
+</view>
+<view wx:if="{{active}}" class="overlay">
+  <view class="sheet">
+    <view class="row">
+      <strong>{{active.title}}</strong>
+      <text bindtap="close">×</text>
+    </view>
+    <view class="detail">
+      📍 {{active.place_name}}
+      <br />
+      🗓 {{active.date}}
+      <br />
+      🐕 {{active.participants}} / {{active.max_people}} 人已报名
+    </view>
+    <view class="desc">{{active.description}}</view>
+    <view wx:if="{{active.host_user_id!==userId}}">
+      <view class="select-title">带哪几只？可以多选</view>
+      <pet-picker pets="{{pets}}" selected="{{selected}}" bind:change="pick" />
+      <button class="primary" bindtap="join">带狗狗报名</button>
+    </view>
+    <button wx:else class="secondary" bindtap="cancel">取消这场约遛</button>
+  </view>
+</view>
+<tab-bar current="/pages/meetups/meetups" />