feat(records): 训练趋势图表 + 列表时长改 MM:SS

- 新增 trend-chart 柱状图组件(CSS,近7天/近6月切换)
- records 页加训练趋势卡片(统计卡片后)
- 训练记录列表时长从秒数改为 MM:SS 显示

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

pages/records/records.js

@@ -19,6 +19,8 @@ Page({
     monthRecords: [],
     historyList: [],
     listMode: 'month',
+    trendMode: 'week',
+    trendData: [],
     showDayDetail: false,
     dayDetail: {},
     icons: iconsMod.build()
@@ -52,7 +54,7 @@ Page({
     storage.validateStreak()
     const stats = storage.getTotalStats()
     const monthKey = `${this.data.currentYear}-${String(this.data.currentMonth).padStart(2, '0')}`
-    const records = storage.getRecordsByMonth(monthKey)
+    const records = (storage.getRecordsByMonth(monthKey) || []).map(r => ({ ...r, durationText: util.formatTime(r.duration) }))
 
     // Each month is already sorted newest-first in storage. To get top 30 most recent,
     // walk months in reverse chrono order and concat — O(months*30) instead of O(n log n).
@@ -61,7 +63,7 @@ Page({
     const historyList = []
     for (const mk of monthKeys) {
       for (const r of byMonth[mk]) {
-        historyList.push(r)
+        historyList.push({ ...r, durationText: util.formatTime(r.duration) })
         if (historyList.length >= 30) break
       }
       if (historyList.length >= 30) break
@@ -80,6 +82,7 @@ Page({
       historyList,
       listMode: this.data.listMode || 'month',
       displayList: (this.data.listMode || 'month') === 'month' ? records : historyList,
+      trendData: this._computeTrend(this.data.trendMode || 'week'),
       loading: false
     })
   },
@@ -115,6 +118,61 @@ Page({
     this.refresh()
   },
 
+  onToggleTrendMode(e) {
+    const mode = e.currentTarget.dataset.mode
+    if (!mode || mode === this.data.trendMode) return
+    this.setData({ trendMode: mode, trendData: this._computeTrend(mode) })
+  },
+
+  /**
+   * 训练趋势数据:
+   *   week  - 近 7 天每天的训练时长(秒)
+   *   month - 近 6 个月每月的训练时长(秒)
+   * 返回 [{ label, value, valueText, highlight }] 供 trend-chart 渲染。
+   */
+  _computeTrend(mode) {
+    const allRecords = Object.values(storage.getRecords()).flat()
+    const today = new Date()
+    const weekdays = ['日', '一', '二', '三', '四', '五', '六']
+    const pad = (n) => String(n).padStart(2, '0')
+
+    if (mode === 'month') {
+      const data = []
+      for (let i = 5; i >= 0; i--) {
+        const d = new Date(today.getFullYear(), today.getMonth() - i, 1)
+        const monthKey = `${d.getFullYear()}-${pad(d.getMonth() + 1)}`
+        const monthRecords = storage.getRecordsByMonth(monthKey) || []
+        const total = monthRecords.reduce((s, r) => s + (Number(r.duration) || 0), 0)
+        data.push({
+          label: `${d.getMonth() + 1}月`,
+          value: total,
+          valueText: total > 0 ? util.formatDuration(total) : '',
+          highlight: i === 0
+        })
+      }
+      return data
+    }
+
+    // default: week (近 7 天)
+    const data = []
+    for (let i = 6; i >= 0; i--) {
+      const d = new Date(today)
+      d.setDate(d.getDate() - i)
+      const dateStr = `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`
+      const total = allRecords
+        .filter((r) => util.dateOnly(r.date) === dateStr)
+        .reduce((s, r) => s + (Number(r.duration) || 0), 0)
+      const isToday = i === 0
+      data.push({
+        label: isToday ? '今天' : weekdays[d.getDay()],
+        value: total,
+        valueText: total > 0 ? util.formatDuration(total) : '',
+        highlight: isToday
+      })
+    }
+    return data
+  },
+
   onDayTap(e) {
     const { year, month, day } = e.detail
     const dateStr = `${year}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`