While sync is in progress the upload button should not be clickable

We are getting a couple complains from users that they can not upload their captures. When diving in deeper it is usually a slow connection and the user keeps clicking on the upload button therefore we could do the following
1. disable the upload button and make it pulse or something obvious.
2. the short "Sync Started" dialogue on the bottom of the screen could have an additional notification such as "this might take some minutes, please be patient" or even something that indicates "your internet connection is slow"

This is really a UI/UX question.

No files, tests, or entry points are named. Start by locating the Android upload button and the brief “Sync Started” dialogue, then trace how sync progress is exposed to the UI; done should include a clear decision on disabling upload during sync and whether to add a patience or slow-connection message.

Written by the indexing model from the issue text.