Identification cleanup (#17301)

# Introduction

following https://github.com/twentyhq/twenty/pull/17279
As we've finally identified all the syncable metadata entities, which
means they're expected to have non nullable applicationId and
universalIdentifier at pg_level we can remove previous retro comp
universalIdentifier fallbacking and update the dto too

~~This needs IdentifyRemainingEntitiesMetadataCommand and
MakeRemainingEntitiesUniversalIdentifierAndApplicationIdNotNullableMigrationCommand
to be run~~
```ts
[Nest] 197  - 01/21/2026, 3:08:35 PM     LOG [MakeRemainingEntitiesUniversalIdentifierAndApplicationIdNotNullableMigrationCommand] Successfully run MakeRemainingEntitiesUniversalIdentifierAndApplicationIdNotNullableMigrationCommand
```

packages/twenty-server/src/engine/metadata-modules/flat-page-layout/utils/transform-page-layout-entity-to-flat-page-layout.util.ts

@@ -13,8 +13,7 @@ export const transformPageLayoutEntityToFlatPageLayout = (
     type: pageLayoutEntity.type,
     objectMetadataId: pageLayoutEntity.objectMetadataId,
     workspaceId: pageLayoutEntity.workspaceId,
-    universalIdentifier:
-      pageLayoutEntity.universalIdentifier ?? pageLayoutEntity.id,
+    universalIdentifier: pageLayoutEntity.universalIdentifier,
     applicationId: pageLayoutEntity.applicationId,
     tabIds: pageLayoutEntity.tabs.map((tab) => tab.id),
   };