Type PageLayout manifest type prop with PageLayoutType (#23375)

Closes #23373

`PageLayoutManifest.type` was typed as `string`, so `definePageLayout({
type: 'NOT_A_VALID_PAGE_LAYOUT_TYPE' })` compiled fine.

It is now typed as `` `${PageLayoutType}` ``, which rejects arbitrary
strings while keeping both forms assignable:

```ts
type: PageLayoutType.STANDALONE_PAGE
type: 'STANDALONE_PAGE'
```

A string enum member is assignable to its own literal type, so ``
PageLayoutType | `${PageLayoutType}` `` would have been the same type as
`` `${PageLayoutType}` `` alone. Going the other way (`type:
PageLayoutType` on its own) is strictly narrower and would break every
app manifest in `packages/twenty-apps` plus the `create-twenty-app`
template, which all pass raw strings.

packages/twenty-docs/developers/extend/apps/layout/page-layouts.mdx

@@ -51,7 +51,7 @@ export default definePageLayout({
 
 ### Key points
 
-- `type` is typically `'RECORD_PAGE'` to customize the detail view of a specific object.
+- `type` is one of `'RECORD_INDEX'`, `'RECORD_PAGE'`, `'DASHBOARD'` or `'STANDALONE_PAGE'`. Use `'RECORD_PAGE'` to customize the detail view of a specific object.
 - `objectUniversalIdentifier` specifies which object this layout applies to.
 - Each `tab` defines a section of the page with a `title`, `position`, and `layoutMode` (`VERTICAL_LIST` for record pages, `GRID` for dashboards). A tab holding a single widget renders it full-bleed automatically; with several widgets they stack as cards.
 - Each `widget` inside a tab can render a [front component](/developers/extend/apps/layout/front-components), a relation list, or other built-in widget types.

packages/twenty-shared/src/application/pageLayoutManifestType.ts

@@ -2,6 +2,7 @@ import { type SyncableEntityOptions } from '@/application/syncableEntityOptionsT
 import {
   type GridPosition,
   type PageLayoutTabLayoutMode,
+  type PageLayoutType,
   type PageLayoutWidgetConditionalDisplay,
   type PageLayoutWidgetUniversalConfiguration,
 } from '@/types';
@@ -26,7 +27,7 @@ export type PageLayoutTabManifest = SyncableEntityOptions & {
 
 export type PageLayoutManifest = SyncableEntityOptions & {
   name: string;
-  type: string;
+  type: `${PageLayoutType}`;
   objectUniversalIdentifier?: string;
   defaultTabToFocusOnMobileAndSidePanelUniversalIdentifier?: string;
   tabs?: PageLayoutTabManifest[];