Add an Electron app drag handle to sign-in page (#3795)

* Add Electron app drag handle to sign-in page

* Don't assign drag regions in web from JSX, results in dev-only console errors about unsupported style values

src/components/AppHeader.tsx

@@ -6,6 +6,7 @@ import { useSettingsAuthContext } from 'hooks/useSettingsAuthContext'
 import styles from './AppHeader.module.css'
 import { RefreshButton } from 'components/RefreshButton'
 import { CommandBarOpenButton } from './CommandBarOpenButton'
+import { isDesktop } from 'lib/isDesktop'
 
 interface AppHeaderProps extends React.PropsWithChildren {
   showToolbar?: boolean
@@ -32,7 +33,9 @@ export const AppHeader = ({
       className={
         'w-full grid ' +
         styles.header +
-        ' overlaid-panes sticky top-0 z-20 px-2 items-start ' +
+        ` ${
+          isDesktop() ? styles.desktopApp + ' ' : ''
+        }overlaid-panes sticky top-0 z-20 px-2 items-start ` +
         className
       }
       style={style}