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/view/entities/view.entity.ts

@@ -17,6 +17,7 @@ import { AggregateOperations } from 'src/engine/api/graphql/graphql-query-runner
 import { UserWorkspaceEntity } from 'src/engine/core-modules/user-workspace/user-workspace.entity';
 import { FieldMetadataEntity } from 'src/engine/metadata-modules/field-metadata/field-metadata.entity';
 import { ObjectMetadataEntity } from 'src/engine/metadata-modules/object-metadata/object-metadata.entity';
+import { ViewFieldGroupEntity } from 'src/engine/metadata-modules/view-field-group/entities/view-field-group.entity';
 import { ViewFieldEntity } from 'src/engine/metadata-modules/view-field/entities/view-field.entity';
 import { ViewFilterGroupEntity } from 'src/engine/metadata-modules/view-filter-group/entities/view-filter-group.entity';
 import { ViewFilterEntity } from 'src/engine/metadata-modules/view-filter/entities/view-filter.entity';
@@ -191,6 +192,12 @@ export class ViewEntity extends SyncableEntity implements Required<ViewEntity> {
   @OneToMany(() => ViewFieldEntity, (viewField) => viewField.view)
   viewFields: Relation<ViewFieldEntity[]>;
 
+  @OneToMany(
+    () => ViewFieldGroupEntity,
+    (viewFieldGroup) => viewFieldGroup.view,
+  )
+  viewFieldGroups: Relation<ViewFieldGroupEntity[]>;
+
   @OneToMany(() => ViewFilterEntity, (viewFilter) => viewFilter.view)
   viewFilters: Relation<ViewFilterEntity[]>;