Extract center column offset, reduce by 20px (#7974)

* extract offset, reduce by 20px

* move constant to `Layout/const.ts`

src/view/shell/desktop/RightNav.tsx

@@ -19,6 +19,7 @@ import {
 } from '#/alf'
 import {AppLanguageDropdown} from '#/components/AppLanguageDropdown'
 import {Divider} from '#/components/Divider'
+import {CENTER_COLUMN_OFFSET} from '#/components/Layout'
 import {InlineLinkText} from '#/components/Link'
 import {ProgressGuideList} from '#/components/ProgressGuide/List'
 import {Text} from '#/components/Typography'
@@ -66,7 +67,7 @@ export function DesktopRightNav({routeName}: {routeName: string}) {
           position: 'fixed',
           left: '50%',
           transform: [
-            {translateX: centerColumnOffset ? 150 : 300},
+            {translateX: 300 + (centerColumnOffset ? CENTER_COLUMN_OFFSET : 0)},
             ...a.scrollbar_offset.transform,
           ],
           width: 300 + gutters.paddingLeft,