Reset Tab Page Layout (#19453)

## Context
- Add "Reset to default" for page layout tabs and widgets — backend
mutation resets overrides, reactivates deactivated children, and deletes
custom children
- Fix override write bug where mutating an overridable property (e.g.
widget title) on a standard-app entity incorrectly overwrote the base
column instead of writing to the overrides JSONB —
PageLayoutUpdateService now uses resolveFlatEntityOverridableProperties
for accurate diffing and routes properties through
sanitizeOverridableEntityInput
- Deprecate isOverridden - We need more time to think about this
feature. Currently this adds too much complexity for a very small
benefit



https://github.com/user-attachments/assets/a84546c8-1e15-4d9e-a489-0825cf8b8ed2

packages/twenty-server/src/engine/metadata-modules/page-layout-widget/utils/from-flat-page-layout-widget-to-page-layout-widget-dto.util.ts

@@ -1,18 +1,22 @@
-import { isDefined } from 'twenty-shared/utils';
-
 import { type FlatPageLayoutWidget } from 'src/engine/metadata-modules/flat-page-layout-widget/types/flat-page-layout-widget.type';
 import { type PageLayoutWidgetDTO } from 'src/engine/metadata-modules/page-layout-widget/dtos/page-layout-widget.dto';
 
 export const fromFlatPageLayoutWidgetToPageLayoutWidgetDto = (
   flatPageLayoutWidget: FlatPageLayoutWidget,
 ): PageLayoutWidgetDTO => {
-  const { createdAt, updatedAt, deletedAt, objectMetadataId, ...rest } =
-    flatPageLayoutWidget;
+  const {
+    createdAt,
+    updatedAt,
+    deletedAt,
+    objectMetadataId,
+    overrides,
+    ...rest
+  } = flatPageLayoutWidget;
 
   return {
     ...rest,
-    isOverridden:
-      isDefined(rest.overrides) && Object.keys(rest.overrides).length > 0,
+    ...(overrides ?? {}),
+    isOverridden: false,
     objectMetadataId: objectMetadataId ?? undefined,
     createdAt: new Date(createdAt),
     updatedAt: new Date(updatedAt),