fix: avatar picker uses chooseMedia, COS domain to tx.vsai.net.cn

- Replace chooseAvatar button with chooseMedia (more reliable, works on all versions)
- COS avatar URL uses tx.vsai.net.cn instead of generated bucket domain
- Phone shows '已授权' only (no actual number displayed)

server/src/routes/user.js

@@ -50,7 +50,7 @@ router.post('/user/avatar', requireUser, upload.single('file'), wrap(async (req,
       ContentType: req.file.mimetype
     }, (err, data) => err ? reject(err) : resolve(data))
   })
-  const avatarUrl = 'https://' + config.cos.bucket + '.cos.' + config.cos.region + '.myqcloud.com/' + key
+  const avatarUrl = 'https://tx.vsai.net.cn/' + key
   await userDao.updateProfile(req.user.user_id, { nickname: null, avatar: avatarUrl, gender: null })
   res.json(ok({ avatar: avatarUrl }))
 }))