feat: payment refund support + admin payment management

- Add refund()/queryRefund()/downloadPlatformCerts() to WechatPayService
- Add refundId field to PaymentOrder schema
- Fix WeChat Pay callback to auto-download platform certs on verification failure
- Fix syncOrder to handle sprint plan properly
- Add admin refund, refund-query, order-detail endpoints
- Add refund UI (button, modal, query) to admin.vue orders tab
- Fix member.vue MP payment: pass outTradeNo instead of prepayId to pollPayResult

zhiyin-app/src/pages/admin/admin.vue

@@ -142,8 +142,10 @@
                 {{ o.status === 'success' ? '已支付' : o.status === 'refunded' ? '已退款' : '待支付' }}
               </view>
               <text class="order-time">{{ o.createdAt ? o.createdAt.slice(0,16).replace('T',' ') : '--' }}</text>
-              <view class="order-actions" v-if="o.status === 'pending'">
-                <text class="sync-btn" @click="syncOrder(o.outTradeNo)">同步</text>
+              <view class="order-actions">
+                <text class="sync-btn" v-if="o.status === 'pending'" @click="syncOrder(o.outTradeNo)">同步</text>
+                <text class="refund-btn" v-if="o.status === 'success'" @click="openRefundModal(o)">退款</text>
+                <text class="sync-btn" v-if="o.status === 'refunded'" @click="queryRefund(o.outTradeNo)">查询</text>
               </view>
             </view>
           </view>
@@ -338,6 +340,29 @@
         </view>
       </view>
 
+      <!-- 退款弹窗 -->
+      <view class="modal-mask" v-if="refundModal.show" @click="closeRefundModal">
+        <view class="modal-content" @click.stop>
+          <text class="modal-title">退款 - {{ refundModal.order?.outTradeNo }}</text>
+          <view class="cfg-row">
+            <text>订单金额</text>
+            <text class="cfg-val">¥{{ ((refundModal.order?.amount || 0) / 100).toFixed(1) }}</text>
+          </view>
+          <view class="cfg-row">
+            <text>退款金额（元）</text>
+            <input class="cfg-input" type="digit" v-model.number="refundAmount" :placeholder="((refundModal.order?.amount || 0) / 100).toFixed(1)" />
+          </view>
+          <view class="cfg-row">
+            <text>退款原因</text>
+            <input class="cfg-input" style="width:300rpx" v-model="refundReason" placeholder="选填" />
+          </view>
+          <view class="modal-actions">
+            <button class="modal-btn cancel" @click="closeRefundModal">取消</button>
+            <button class="modal-btn confirm" style="background:#EF4444" @click="doRefund">确认退款</button>
+          </view>
+        </view>
+      </view>
+
       <!-- 管理员 -->
       <view v-if="tab === 'admins'" class="section">
         <view class="search-bar">
@@ -448,6 +473,67 @@ const creditTypes = ref([
   { key: 'shareCredits', label: '分享积分', value: 0 },
 ])
 
+// Refund modal
+const refundModal = ref({ show: false, order: null })
+const refundAmount = ref(0)
+const refundReason = ref('')
+
+const openRefundModal = (order) => {
+  refundModal.value = { show: true, order }
+  refundAmount.value = order.amount / 100
+  refundReason.value = ''
+}
+
+const closeRefundModal = () => {
+  refundModal.value = { show: false, order: null }
+}
+
+const doRefund = async () => {
+  const order = refundModal.value.order
+  if (!order) return
+  uni.showModal({
+    title: '确认退款', content: `确定对订单 ${order.outTradeNo} 退款 ¥${refundAmount.value.toFixed(1)}？`,
+    success: async (r) => {
+      if (!r.confirm) return
+      try {
+        const res = await apiAdmin('/order/refund', {
+          method: 'POST',
+          body: { outTradeNo: order.outTradeNo, amount: Math.round(refundAmount.value * 100), reason: refundReason.value },
+        })
+        if (res.statusCode === 200) {
+          uni.showToast({ title: '退款成功', icon: 'success' })
+          closeRefundModal()
+          loadOrders()
+        } else {
+          uni.showToast({ title: res.data?.message || '退款失败', icon: 'none' })
+        }
+      } catch (e) {
+        uni.showToast({ title: '退款失败', icon: 'none' })
+      }
+    },
+  })
+}
+
+const queryRefund = async (outTradeNo) => {
+  uni.showToast({ title: '查询中...', icon: 'none' })
+  try {
+    const res = await apiAdmin('/order/refund/' + outTradeNo)
+    if (res.statusCode === 200) {
+      const wx = res.data.wxRefund
+      if (wx) {
+        uni.showModal({
+          title: '退款状态',
+          content: `微信状态: ${wx.status || '--'}\n退款金额: ¥${(wx.amount?.refund || 0) / 100}\n建议以微信侧为准`,
+        })
+      } else {
+        uni.showToast({ title: '本地状态: ' + (res.data.localStatus || '--'), icon: 'none' })
+      }
+    } else {
+      uni.showToast({ title: '查询失败', icon: 'none' })
+    }
+  } catch { uni.showToast({ title: '查询失败', icon: 'none' }) }
+}
+
 const token = () => uni.getStorageSync('token') || ''
 
 const apiAdmin = (path, opts = {}) => {
@@ -860,6 +946,7 @@ onMounted(() => { doVerify() })
 .order-time { font-size: 20rpx; color: var(--color-text-tertiary); flex: 1; text-align: right; }
 .order-actions { }
 .sync-btn { font-size: 20rpx; color: var(--color-primary); padding: 4rpx 12rpx; border: 2rpx solid var(--color-primary); border-radius: var(--radius-round); }
+.refund-btn { font-size: 20rpx; color: #EF4444; padding: 4rpx 12rpx; border: 2rpx solid #EF4444; border-radius: var(--radius-round); }
 .config-card { background: #FFF; border-radius: var(--radius-sm); padding: 20rpx; margin-bottom: 12rpx; }
 .cfg-title { font-size: 24rpx; font-weight: 600; color: var(--color-text); margin-bottom: 12rpx; }
 .cfg-row { display: flex; justify-content: space-between; padding: 8rpx 0; font-size: 22rpx; color: var(--color-text-secondary); align-items: center; }