fix: 振动定时器清理、完成保存守卫、暗黑冷启动、头像云存储

- timer: 振动 setTimeout 入栈追踪,暂停/停止/卸载/重练统一清理,
  避免页面销毁后残留震动(_clearVibrateTimers)
- timer: _saving 守卫统一到 _saveAndShowCompletion,自然完成与手动
  结束两路径都防重复保存;修复 onTrainAgain 不重置会话状态导致
  再练一次后第二次无语音/振动且保存被挡
- app.wxss: @media dark 补全 --text/--card-bg/--bg-soft/--border/
  --success/--danger,冷启动即为完整深色,不再背景深卡片白的割裂闪烁
- settings: 头像优先上传云存储存 fileID,三级回退(fileID->base64->
  临时URL),pushAll 不再每次传输图片字节

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

pages/settings/settings.js

@@ -140,31 +140,46 @@ Page({
   async onChooseAvatar(e) {
     const avatarUrl = e.detail.avatarUrl
     if (!avatarUrl) return
+
+    // Store the avatar durably. Prefer a cloud-storage fileID: it keeps the
+    // profile doc small and avoids re-transferring the image bytes on every
+    // pushAll. Fall back to an inline base64 data URI if cloud storage is
+    // unavailable, and to the raw temp URL as a last resort.
+    let permanentUrl = null
     try {
-      // chooseAvatar returns a wxfile:// temporary URL that expires in a few
-      // days. Read the bytes and store as a data URI so the avatar survives
-      // long-term. Falls back to the raw URL on size/read error.
-      const permanentUrl = await util.fileToDataURI(avatarUrl)
-      this.setData({ avatarUrl: permanentUrl })
-      const saved = storage.saveProfile({
-        nickname: this.data.nickName,
-        avatarUrl: permanentUrl
-      })
-      this.setData({
-        nickName: saved.nickname || this.data.nickName,
-        avatarUrl: saved.avatarUrl
-      })
-      wx.showToast({ title: '头像已更新', icon: 'success', duration: 1200 })
+      permanentUrl = await this._uploadAvatar(avatarUrl)
     } catch (err) {
-      console.warn('avatar convert failed, saving temp URL:', err)
-      // Fallback: save the raw wxfile URL. Will eventually expire.
-      this.setData({ avatarUrl })
-      storage.saveProfile({
-        nickname: this.data.nickName,
-        avatarUrl
-      })
-      wx.showToast({ title: '头像已更新', icon: 'success', duration: 1200 })
+      console.warn('[avatar] cloud upload failed, trying base64:', err)
+      try {
+        permanentUrl = await util.fileToDataURI(avatarUrl)
+      } catch (err2) {
+        console.warn('[avatar] base64 convert failed, saving temp URL:', err2)
+        permanentUrl = avatarUrl
+      }
     }
+
+    this.setData({ avatarUrl: permanentUrl })
+    const saved = storage.saveProfile({
+      nickname: this.data.nickName,
+      avatarUrl: permanentUrl
+    })
+    this.setData({
+      nickName: saved.nickname || this.data.nickName,
+      avatarUrl: saved.avatarUrl
+    })
+    wx.showToast({ title: '头像已更新', icon: 'success', duration: 1200 })
+  },
+
+  /**
+   * Upload the chosen avatar to cloud storage and return its fileID.
+   * Throws if cloud is disabled or the upload fails - caller falls back.
+   */
+  async _uploadAvatar(filePath) {
+    if (!cloud.enabled) throw new Error('cloud not enabled')
+    const cloudPath = `avatar/${Date.now()}-${Math.floor(Math.random() * 1e6)}.png`
+    const res = await wx.cloud.uploadFile({ cloudPath, filePath })
+    if (!res || !res.fileID) throw new Error('uploadFile returned no fileID')
+    return res.fileID
   },
 
   onNicknameBlur(e) {