feat(timer): 训练时长低于阈值不记录并明确提示

- config.js 新增 minRecordSeconds: 20 阈值配置，改配置即可调整门槛
- timer.js: finishTraining/_onCircuitComplete 低时长不播完成语音;
  _saveAndShowCompletion 兜底判断,任何入口都不会把短时训练落库;
  新增 _showNotRecorded: 不保存记录、不更新连胜,复用完成弹窗展示实际秒数
- timer.wxml/wxss: 完成弹窗新增"未计入记录"提示行(门槛说明),
  未记录时隐藏"查看记录/分享"按钮,只留"再来一次+回到首页"
- 修复状态残留: 未记录后点"再来一次",下次正常完成不会误显示"未计入记录"

pages/timer/timer.wxss

@@ -425,6 +425,46 @@
   height: 32rpx;
 }
 
+/* 未达最低记录时长提示(完成弹窗内):主色淡底信息块,与科学提示同风格 */
+.completion-not-recorded {
+  display: flex;
+  flex-direction: column;
+  gap: 10rpx;
+  width: 100%;
+  box-sizing: border-box;
+  background: rgba(var(--primary-rgb), 0.08);
+  border-radius: 20rpx;
+  padding: 20rpx 24rpx;
+  margin-bottom: 28rpx;
+  animation: tipIn 0.4s ease 0.5s both;
+}
+
+.completion-not-recorded-main {
+  display: flex;
+  align-items: center;
+  gap: 10rpx;
+}
+
+.completion-not-recorded-icon {
+  width: 32rpx;
+  height: 32rpx;
+  flex-shrink: 0;
+}
+
+.completion-not-recorded-title {
+  flex: 1;
+  font-size: 26rpx;
+  font-weight: 600;
+  line-height: 1.4;
+  color: var(--primary);
+}
+
+.completion-not-recorded-sub {
+  font-size: 24rpx;
+  line-height: 1.5;
+  color: var(--text-secondary);
+}
+
 .streak-text {
   font-weight: 500;
 }