Introducing view field group syncable entity (#17867)

## Context
Introduces a new viewFieldGroup entity that allows grouping view fields
into sections (e.g. "General", "Additional", "Other") within a view.

The page layout fields widget needs a way to organize fields into
sections. Today, views have no concept of field grouping. This PR
introduces the viewFieldGroup entity which sits between a view and its
viewFields, enabling section-based organization.

<img width="401" height="724" alt="Layout - V2 (customize visibility)"
src="https://github.com/user-attachments/assets/6376e2ab-44db-42bf-9d2c-758f56f6b548"
/>

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/engine/metadata-modules/object-metadata/object-metadata.service.ts

@@ -549,6 +549,7 @@ export class ObjectMetadataService extends TypeOrmQueryService<ObjectMetadataEnt
       visibility: ViewVisibility.WORKSPACE,
       createdByUserWorkspaceId: null,
       viewFieldUniversalIdentifiers: [],
+      viewFieldGroupUniversalIdentifiers: [],
       viewFilterUniversalIdentifiers: [],
       viewGroupUniversalIdentifiers: [],
       viewFilterGroupUniversalIdentifiers: [],
@@ -580,6 +581,7 @@ export class ObjectMetadataService extends TypeOrmQueryService<ObjectMetadataEnt
       .map<UniversalFlatViewField>((field, index) => ({
         fieldMetadataUniversalIdentifier: field.universalIdentifier,
         viewUniversalIdentifier,
+        viewFieldGroupUniversalIdentifier: null,
         createdAt,
         updatedAt: createdAt,
         deletedAt: null,