fix: Remove incorrect background logic from PageLayoutGridLayout (#16945)

Removes the background color logic that was incorrectly added to
PageLayoutGridLayout in PR #16870. Grid layouts are only used for
dashboards where widgets have their own background colors set in
WidgetCard.tsx, so the container background was causing visual
mismatches in padding/gap areas. The background logic remains correctly
applied in PageLayoutVerticalListViewer and PageLayoutVerticalListEditor
where widgets need to inherit the container background.

---------

Co-authored-by: Devessier <baptiste@devessier.fr>

packages/twenty-front/src/modules/page-layout/hooks/usePageLayoutShouldUseWhiteBackground.ts

@@ -0,0 +1,13 @@
+import { useLayoutRenderingContext } from '@/ui/layout/contexts/LayoutRenderingContext';
+import { useIsMobile } from '@/ui/utilities/responsive/hooks/useIsMobile';
+import { PageLayoutType } from '~/generated/graphql';
+
+export const usePageLayoutShouldUseWhiteBackground = () => {
+  const isMobile = useIsMobile();
+  const { isInRightDrawer, layoutType } = useLayoutRenderingContext();
+
+  const shouldUseWhiteBackground =
+    layoutType === PageLayoutType.RECORD_PAGE && (isMobile || isInRightDrawer);
+
+  return { shouldUseWhiteBackground };
+};

packages/twenty-front/src/modules/page-layout/hooks/useShouldUseWhiteBackground.ts

@@ -1,14 +0,0 @@
-import { useIsInPinnedTab } from '@/page-layout/widgets/hooks/useIsInPinnedTab';
-import { useLayoutRenderingContext } from '@/ui/layout/contexts/LayoutRenderingContext';
-import { useIsMobile } from '@/ui/utilities/responsive/hooks/useIsMobile';
-
-export const useShouldUseWhiteBackground = () => {
-  const isMobile = useIsMobile();
-  const { isInRightDrawer } = useLayoutRenderingContext();
-  const { isInPinnedTab } = useIsInPinnedTab();
-
-  const shouldUseWhiteBackground =
-    (isMobile || isInRightDrawer) && !isInPinnedTab;
-
-  return { shouldUseWhiteBackground };
-};