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/flat-object-metadata/utils/recompute-view-field-identifier-after-flat-object-identifier-update.util.ts

@@ -80,6 +80,8 @@ export const recomputeViewFieldIdentifierAfterFlatObjectIdentifierUpdate = ({
         deletedAt: null,
         universalIdentifier: viewFieldId,
         aggregateOperation: null,
+        viewFieldGroupId: null,
+        viewFieldGroupUniversalIdentifier: null,
         applicationId: existingFlatObjectMetadata.applicationId,
         applicationUniversalIdentifier:
           existingFlatObjectMetadata.applicationUniversalIdentifier,