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/app.wxss

@@ -486,6 +486,84 @@ button.btn::after {
   color: #f2f7ff;
 }
 
+/* 运营报告样式 */
+.report-modal {
+  margin-top: 20rpx;
+  padding: 24rpx;
+  border-radius: 24rpx;
+  background: linear-gradient(145deg, rgba(24, 47, 78, 0.95), rgba(16, 31, 53, 0.98));
+  border: 1rpx solid rgba(139, 177, 223, 0.35);
+  position: relative;
+}
+
+.report-header {
+  text-align: center;
+  margin-bottom: 16rpx;
+}
+
+.report-title {
+  font-size: 32rpx;
+  font-weight: 700;
+  color: #eff6ff;
+}
+
+.report-period {
+  font-size: 22rpx;
+  color: var(--sub);
+  margin-top: 6rpx;
+}
+
+.report-close {
+  position: absolute;
+  top: 16rpx;
+  right: 16rpx;
+  width: 40rpx;
+  height: 40rpx;
+  border-radius: 50%;
+  background: rgba(255, 91, 111, 0.2);
+  color: #ffdce1;
+  font-size: 28rpx;
+  text-align: center;
+  line-height: 40rpx;
+}
+
+.report-section {
+  margin-top: 16rpx;
+  padding: 16rpx;
+  border-radius: 16rpx;
+  background: rgba(17, 35, 58, 0.6);
+}
+
+.report-section-title {
+  font-size: 26rpx;
+  font-weight: 600;
+  color: #dceeff;
+  margin-bottom: 12rpx;
+}
+
+.report-kpi {
+  padding: 12rpx;
+  border-radius: 12rpx;
+  background: rgba(19, 40, 66, 0.7);
+  text-align: center;
+}
+
+.report-kpi-value {
+  font-size: 28rpx;
+  font-weight: 700;
+  color: #f2f7ff;
+}
+
+.report-kpi-label {
+  font-size: 20rpx;
+  color: var(--sub);
+  margin-top: 4rpx;
+}
+
+.report-trend-item {
+  margin-top: 8rpx;
+}
+
 .chip-group {
   display: flex;
   flex-wrap: wrap;