Add is active to overridable entities and deactivation logic for page layouts (#19200)

- Replace soft-deletion (deletedAt) with isActive boolean for
overridable entities (tabs, widgets, viewFieldGroups, viewFields).
Standard entities are deactivated (isActive: false) when removed from
update payloads, while custom entities are hard-deleted.
- When a viewFieldGroup is deactivated/deleted, its viewFields are
reassigned to the next section by position (or null if none remain).
- Add isActive: true filters to viewFieldGroup and viewField API queries
so deactivated entities are excluded from responses.

Next: 
- fields-widget-upsert.service.ts should be refactored a bit
- Add restore logic

packages/twenty-server/src/engine/metadata-modules/view/utils/compute-fields-widget-view-fields-and-groups-to-create.util.ts

@@ -62,6 +62,7 @@ export const computeFieldsWidgetViewFieldsAndGroupsToCreate = ({
     name: 'General',
     position: 0,
     isVisible: true,
+    isActive: true,
     overrides: null,
     viewFieldUniversalIdentifiers: [],
     createdAt,
@@ -83,6 +84,7 @@ export const computeFieldsWidgetViewFieldsAndGroupsToCreate = ({
       deletedAt: null,
       universalIdentifier: v4(),
       isVisible,
+      isActive: true,
       size: DEFAULT_VIEW_FIELD_SIZE,
       position: index,
       aggregateOperation: null,
@@ -101,6 +103,7 @@ export const computeFieldsWidgetViewFieldsAndGroupsToCreate = ({
       name: 'Other',
       position: 1,
       isVisible: true,
+      isActive: true,
       overrides: null,
       viewFieldUniversalIdentifiers: [],
       createdAt,
@@ -122,6 +125,7 @@ export const computeFieldsWidgetViewFieldsAndGroupsToCreate = ({
         deletedAt: null,
         universalIdentifier: v4(),
         isVisible,
+        isActive: true,
         size: DEFAULT_VIEW_FIELD_SIZE,
         position: index,
         aggregateOperation: null,