Refactor auth form styles

Closes #4246

- Removed the input wrapper background colour
- Moved `:focus` styles to one element, so its not defined separate for each page
- Removed unnecessary MQ for body background colour (it changed nothing)
Merge pull request #4249 from PaulAdamDavis/fix-signin-styles

Refactor auth form styles
Update component indents & new lines
Component closing tag comments
Layout spacing & comments
Pattern spacing & comments