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/core-modules/application/application-manifest/converters/from-page-layout-tab-manifest-to-universal-flat-page-layout-tab.util.ts

@@ -23,6 +23,7 @@ export const fromPageLayoutTabManifestToUniversalFlatPageLayoutTab = ({
     icon: pageLayoutTabManifest.icon ?? null,
     layoutMode:
       pageLayoutTabManifest.layoutMode ?? PageLayoutTabLayoutMode.GRID,
+    isActive: true,
     widgetUniversalIdentifiers: [],
     createdAt: now,
     updatedAt: now,

packages/twenty-server/src/engine/core-modules/application/application-manifest/converters/from-page-layout-widget-manifest-to-universal-flat-page-layout-widget.util.ts

@@ -19,6 +19,7 @@ export const fromPageLayoutWidgetManifestToUniversalFlatPageLayoutWidget = ({
     applicationUniversalIdentifier,
     pageLayoutTabUniversalIdentifier,
     title: pageLayoutWidgetManifest.title,
+    isActive: true,
     type: pageLayoutWidgetManifest.type as WidgetType,
     objectMetadataUniversalIdentifier:
       pageLayoutWidgetManifest.objectUniversalIdentifier ?? null,

packages/twenty-server/src/engine/core-modules/application/application-manifest/converters/from-view-field-group-manifest-to-universal-flat-view-field-group.util.ts

@@ -20,6 +20,7 @@ export const fromViewFieldGroupManifestToUniversalFlatViewFieldGroup = ({
     name: viewFieldGroupManifest.name ?? '',
     position: viewFieldGroupManifest.position,
     isVisible: viewFieldGroupManifest.isVisible ?? true,
+    isActive: true,
     overrides: null,
     viewFieldUniversalIdentifiers: [],
     createdAt: now,

packages/twenty-server/src/engine/core-modules/application/application-manifest/converters/from-view-field-manifest-to-universal-flat-view-field.util.ts

@@ -22,6 +22,7 @@ export const fromViewFieldManifestToUniversalFlatViewField = ({
     viewFieldGroupUniversalIdentifier:
       viewFieldManifest.viewFieldGroupUniversalIdentifier ?? null,
     isVisible: viewFieldManifest.isVisible ?? true,
+    isActive: true,
     size: viewFieldManifest.size ?? 0,
     position: viewFieldManifest.position,
     aggregateOperation: viewFieldManifest.aggregateOperation ?? null,