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>

utils/plan.js

@@ -73,8 +73,8 @@ const getPlan = (planId, customPlans) => {
   return plans[planId] || plans.beginner
 }
 
-const getTodayTarget = (planId, currentDay) => {
-  const plan = getPlan(planId)
+const getTodayTarget = (planId, currentDay, customPlans) => {
+  const plan = getPlan(planId, customPlans)
   // 防御:计划数据损坏(planId 无效 / days 为空)时直接返回 0,
   // 避免 plan.days[0] 为 undefined 后访问 .target 抛出崩溃。
   if (!plan.days || plan.days.length === 0) return 0