fix(sync): show Sync brand name when signin up/in for Sync

Fixes #1339.

WIP, we might need string changes.
The entire string needs to be localizable, so localizers can change order if needed.

For more details, please have a look at: https://developer.mozilla.org/en-US/docs/Web_Localizability/Creating_localizable_web_applications#...but_don%27t_sacrifice_flexibility

Thanks for bringing this up!