feat: 个人最佳趋势改为折线图 + 底部最佳趋势日期 + 修复

- 趋势组件 trend-chart 新增 chartType(line/bar),line 模式用内联 SVG 渲染折线+渐变面积(无 canvas)
- 记录页个人最佳趋势改用折线图,峰值信息移到图表下方对称高亮块显示最佳趋势产生日期
- 修复1: linePoints 漏存绝对坐标 y 导致运行时 toFixed 崩溃
- 修复2: 折线模式漏渲染数据点数值(valueText),现圆点上方显示且 0 值不显示

components/trend-chart/trend-chart.wxss

@@ -92,3 +92,80 @@
   color: var(--primary);
   font-weight: 600;
 }
+
+/* ---- Line mode ---- */
+.trend-chart.line {
+  /* extra top room so the value caption above the highest dot isn't clipped */
+  padding-top: 30rpx;
+}
+
+.trend-line {
+  position: relative;
+  width: 100%;
+}
+
+.trend-line-img {
+  display: block;
+  width: 100%;
+}
+
+.trend-line-dot {
+  position: absolute;
+  width: 16rpx;
+  height: 16rpx;
+  margin-left: -8rpx;
+  margin-top: -8rpx;
+  border-radius: 50%;
+  background: var(--primary);
+  border: 3rpx solid var(--card-bg, #FFFFFF);
+  box-sizing: border-box;
+}
+
+.trend-chart.peak .trend-line-dot {
+  background: var(--primary);
+}
+
+.trend-line-dot.highlight {
+  width: 20rpx;
+  height: 20rpx;
+  margin-left: -10rpx;
+  margin-top: -10rpx;
+  box-shadow: 0 0 14rpx rgba(var(--primary-rgb), 0.6);
+}
+
+/* value caption floats above the dot so it never eats into the line */
+.trend-line-value {
+  position: absolute;
+  bottom: 100%;
+  left: 50%;
+  transform: translateX(-50%);
+  margin-bottom: 6rpx;
+  font-size: 16rpx;
+  color: var(--text-secondary);
+  line-height: 1;
+  white-space: nowrap;
+}
+
+.trend-line-dot.highlight .trend-line-value {
+  color: var(--primary);
+  font-weight: 600;
+}
+
+.trend-line-labels {
+  position: relative;
+  height: 28rpx;
+  margin-top: 10rpx;
+}
+
+.trend-line-label {
+  position: absolute;
+  transform: translateX(-50%);
+  font-size: 20rpx;
+  color: var(--text-secondary);
+  white-space: nowrap;
+}
+
+.trend-line-label.highlight {
+  color: var(--primary);
+  font-weight: 600;
+}