Disable reset to default when custom tab or widget (#19814)

## Context
"Reset to default" action is rejected by the backend for custom entities
because there is no "default" concept for them

## Implementation
Grey out the Reset to default action on record page-layout tabs and
widgets when the entity either has no applicationId yet (unsaved draft —
previously slipped through the existing check), or belongs to the
workspace custom application.

<img width="926" height="370" alt="Screenshot 2026-04-17 at 18 50 31"
src="https://github.com/user-attachments/assets/c7c163f4-17a6-4b69-a66d-90f9085d27a2"
/>

packages/twenty-front/src/modules/page-layout/components/__stories__/PageLayoutRenderer.stories.tsx

@@ -75,6 +75,7 @@ const mixedGraphsPageLayoutMocks = {
       widgets: [
         {
           __typename: 'PageLayoutWidget',
+          applicationId: '',
           isActive: true,
           id: 'number-widget',
           pageLayoutTabId: 'mixed-tab',
@@ -100,6 +101,7 @@ const mixedGraphsPageLayoutMocks = {
         } satisfies PageLayoutWidget,
         {
           __typename: 'PageLayoutWidget',
+          applicationId: '',
           isActive: true,
           id: 'gauge-widget',
           pageLayoutTabId: 'mixed-tab',
@@ -126,6 +128,7 @@ const mixedGraphsPageLayoutMocks = {
         } satisfies PageLayoutWidget,
         {
           __typename: 'PageLayoutWidget',
+          applicationId: '',
           isActive: true,
           id: 'pie-widget',
           pageLayoutTabId: 'mixed-tab',
@@ -153,6 +156,7 @@ const mixedGraphsPageLayoutMocks = {
         } satisfies PageLayoutWidget,
         {
           __typename: 'PageLayoutWidget',
+          applicationId: '',
           isActive: true,
           id: 'bar-widget',
           pageLayoutTabId: 'mixed-tab',