move sign in labels to be above inputs (#28753)

move sign in labels to be above inputs (#28753)

There are a few inconsistencies within Gitea and this PR addresses one of them.
This PR updates the sign-in page layout, including the register and openID tabs,
to match the layout of the settings pages (`/user/settings`) for more consistency.

**Before**
<img width="968" alt="Screenshot 2024-02-05 at 8 27 24 AM"
src="https://github.com/go-gitea/gitea/assets/6152817/fb0cb517-57c0-4eed-be1d-56f36bd1960d">

**After**
<img width="968" alt="Screenshot 2024-02-05 at 8 26 39 AM"
src="https://github.com/go-gitea/gitea/assets/6152817/428d691d-0a42-4a67-a646-05527f2a7b41">

---------

Co-authored-by: rafh <rafaelheard@gmail.com>