fix: 修复 4 个正确性问题(分享秒数/主题同步/云推送定位/streak重算)

- timer: 完成弹窗存实际时长 completionActualElapsed,分享改用它,避免用动画值导致秒数错误
- theme: setTheme 补 _markLocalChanged,避免云恢复覆盖未同步的主题改动
- cloud: _doPush 重定位查询补 orderBy(updatedAt desc),与 pullAll 一致,避免命中最旧文档
- storage: deleteRecord 改用 recomputeStreak,修复删连续链中间某天 streak 虚高

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

utils/storage.js

@@ -96,8 +96,8 @@ const deleteRecord = (recordId) => {
   })
   if (!found) return  // id not found, don't overwrite storage
   wx.setStorageSync(RECORDS_KEY, records)
-  // Re-validate streak: deleting the last record for a day should break the streak
-  validateStreak()
+  // 重新计算连续打卡:删连续链中间某天会断链,validateStreak 只在 lastDate 被删时重算,不够
+  recomputeStreak()
   cloud.pushAll()
 }
 
@@ -435,6 +435,7 @@ module.exports = {
   validateStreak,
   recomputeStreak,
   updateStreak,
+  _markLocalChanged,
   getToday,
   getDateOffset,
   getTodayRecord