feat: 运营报告生成功能

- 后端新增 /admin/stats/report 接口，生成14天运营数据报告
- 报告内容：垃圾信息变化趋势、高频风险词Top10、误判率趋势
- 前端运营看板增加"生成报告"按钮，展示完整报告
- 支持复制报告文本到剪贴板

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

miniprogram/pages/admin-dashboard/index.wxml

@@ -54,4 +54,83 @@
       <text class="tag" wx:for="{{topKeywords}}" wx:key="token">{{item.token}} × {{item.count}}</text>
     </view>
   </view>
+
+  <!-- 生成报告按钮 -->
+  <view class="card fade-up fade-up-delay-3">
+    <button class="btn btn-accent" loading="{{reportLoading}}" bindtap="generateReport">生成运营报告</button>
+  </view>
+
+  <!-- 报告展示区域 -->
+  <view class="report-modal" wx:if="{{report}}">
+    <view class="report-header">
+      <view class="report-title">垃圾信息运营报告</view>
+      <view class="report-period">{{report.period}}</view>
+    </view>
+
+    <view class="report-close" bindtap="closeReport">×</view>
+
+    <view class="report-section">
+      <view class="report-section-title">汇总统计</view>
+      <view class="grid-3">
+        <view class="report-kpi">
+          <view class="report-kpi-value">{{report.summary.total_posts}}</view>
+          <view class="report-kpi-label">总发布量</view>
+        </view>
+        <view class="report-kpi">
+          <view class="report-kpi-value">{{report.summary.total_blocked}}</view>
+          <view class="report-kpi-label">拦截量</view>
+        </view>
+        <view class="report-kpi">
+          <view class="report-kpi-value">{{report.summary.total_published}}</view>
+          <view class="report-kpi-label">正常发布</view>
+        </view>
+      </view>
+      <view class="row">
+        <text class="label">拦截率</text>
+        <text class="value">{{report.summary.blocked_ratio * 100}}%</text>
+      </view>
+      <view class="row">
+        <text class="label">平均误判率</text>
+        <text class="value">{{report.summary.avg_misjudge_rate_text}}</text>
+      </view>
+    </view>
+
+    <view class="report-section">
+      <view class="report-section-title">垃圾信息数量变化（近14天）</view>
+      <view class="report-trend-item" wx:for="{{report.spam_trend}}" wx:key="date">
+        <view class="row">
+          <text class="label">{{item.label}}</text>
+          <text class="value">拦截 {{item.blocked}} / 发布 {{item.published}}</text>
+        </view>
+        <view class="progress-track">
+          <view class="progress-fill" style="width: {{item.blocked_percent}};"></view>
+        </view>
+      </view>
+    </view>
+
+    <view class="report-section">
+      <view class="report-section-title">高频风险词 Top10</view>
+      <view class="chip-group">
+        <text class="tag tag-danger" wx:for="{{report.topKeywords}}" wx:for-item="kw" wx:if="{{index < 10}}" wx:key="token">{{kw.token}} × {{kw.count}}</text>
+      </view>
+    </view>
+
+    <view class="report-section">
+      <view class="report-section-title">误判率趋势（近14天）</view>
+      <view class="report-trend-item" wx:for="{{report.misjudge_trend}}" wx:key="date">
+        <view class="row">
+          <text class="label">{{item.label}}</text>
+          <text class="value">{{item.misjudge_rate_text}}</text>
+        </view>
+        <view class="progress-track">
+          <view class="progress-fill-safe" style="width: {{item.rate_percent}};"></view>
+        </view>
+      </view>
+    </view>
+
+    <view class="btn-row">
+      <button class="btn btn-primary" bindtap="copyReportText">复制报告文本</button>
+      <button class="btn btn-ghost" bindtap="closeReport">关闭</button>
+    </view>
+  </view>
 </view>