fix(electron): app fallback styles (#8225)

packages/frontend/apps/electron/renderer/app.css.ts

@@ -0,0 +1,5 @@
+import { style } from '@vanilla-extract/css';
+
+export const fallback = style({
+  paddingTop: 52,
+});

packages/frontend/apps/electron/renderer/shell/shell.css.ts

@@ -18,14 +18,13 @@ export const root = style({
 
 export const appTabsHeader = style({
   zIndex: 1,
+  position: 'absolute',
+  top: 0,
 });
 
 export const fallbackRoot = style({
-  position: 'absolute',
-  paddingTop: 52,
   width: '100%',
   height: '100%',
-  zIndex: 0,
 });
 
 export const splitViewFallback = style({