fix: 修复审查发现的 4 个高优先级问题

- plan: getTodayTarget 补 customPlans 参数,timer/index 调用点传值,修复自定义计划每日目标失效
- leaderboard: fetchRank 加请求序列号丢弃过期响应,修复快速切换周期竞态
- leaderboard 云函数:遍历记录加防御(r.date/duration/数组校验),避免单条脏数据崩溃全榜
- tts: _upload cloudPath 补 volume/speed,避免不同音量语速音频互相覆盖

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

pages/leaderboard/leaderboard.js

@@ -54,14 +54,19 @@ Page({
   },
 
   fetchRank(cb) {
+    // 序列号:快速切换周期时丢弃旧响应,避免旧 period 的数据覆盖新 period
+    this._fetchSeq = (this._fetchSeq || 0) + 1
+    const seq = this._fetchSeq
+    const period = this.data.activePeriod
     this.setData({ loading: true, empty: false })
     wx.cloud.callFunction({
       name: 'leaderboard',
       data: {
-        period: this.data.activePeriod,
+        period,
         maxRank: config.leaderboardMaxRank
       }
     }).then(res => {
+      if (seq !== this._fetchSeq) { if (cb) cb(); return }  // 过期响应,丢弃
       this._applyResult(res.result || {})
       if (cb) cb()
     }).catch((err) => {
@@ -70,6 +75,7 @@ Page({
       // normal (user didn't train today), and a toast would mislead
       // them into thinking the cloud is broken.
       console.warn('[leaderboard] cloud function failed, using local fallback:', err)
+      if (seq !== this._fetchSeq) { if (cb) cb(); return }
       this._applyLocal()
       if (cb) cb()
     })