fix(vibrate): 修复旧用户震动失效 + 新增震动强度选项

根因:user_settings 早期无 vibrate 字段,getSettings 未兜底,
_remind 的 !s.vibrate 误判 undefined 为关闭,导致震动静默失效,
需手动操作开关才恢复。

- storage: getSettings 兜底 vibrate/voiceGuide/vibrateIntensity 默认值
- timer: !s.vibrate 改 === false,字段缺失视为开(与 voiceGuide 一致)
- timer: vibrate 按 vibrateIntensity 选 API(light/medium=vibrateShort,
  heavy=vibrateLong),fail 回调辅助排查
- settings: 新增"震动强度"三档(短促/标准/强烈),默认强烈

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pages/timer/timer.js

@@ -132,13 +132,27 @@ Page({
     const s = storage.getSettings()
     const { remaining, elapsed, duration } = tick
     const vibrate = (n, ms) => {
-      if (!s.vibrate) return
+      // `=== false` (not `!s.vibrate`) so an undefined field (legacy users
+      // whose settings predate the toggle) is treated as ON, matching the
+      // voiceGuide check below. `!s.vibrate` used to see undefined as falsy
+      // and silently skip vibration until the user toggled the switch.
+      if (s.vibrate === false) return
+      const intensity = s.vibrateIntensity || 'heavy'
+      // light/medium = vibrateShort(type); heavy = vibrateLong(400ms).
+      // vibrateLong is the most reliable on iOS real devices; the short
+      // types are nicer but may be silent on some devices - user picks.
+      const doVibrate = () => {
+        const fail = (err) => console.warn('[vibrate] failed:', err.errMsg || err)
+        if (intensity === 'light') wx.vibrateShort({ type: 'light', fail })
+        else if (intensity === 'medium') wx.vibrateShort({ type: 'medium', fail })
+        else wx.vibrateLong({ fail })
+      }
       try {
         for (let i = 0; i < n; i++) {
           // Track timers so pause/stop/unload can cancel pending bursts
           // instead of firing vibrations on a page that's already torn down.
           const id = setTimeout(() => {
-            wx.vibrateShort()
+            doVibrate()
             const idx = this._vibrateTimers.indexOf(id)
             if (idx > -1) this._vibrateTimers.splice(idx, 1)
           }, i * (ms + 30))