[FRONT COMPONENTS] Headless components (#18096)

## Description

- Add `isHeadless` field to `FrontComponent` entity so front components
can run without rendering UI in the command menu
- Introduce headless front component mounting logic:
`HeadlessFrontComponentMountRoot` at the application root,
`useMountHeadlessFrontComponent`, and `useUnmountHeadlessFrontComponent`
hooks to mount/unmount headless components
- Expand the SDK with new action components (`Action`, `ActionLink`,
`ActionOpenSidePanelPage`) and host communication functions
(`openSidePanelPage`, `unmountFrontComponent`)
- Move `CommandMenuPages` type to twenty-shared so the SDK can reference
it for side panel navigation

## Video QA



https://github.com/user-attachments/assets/4f9e3bb1-fcd1-42be-b3f4-a97e80c2add2

packages/twenty-front/src/modules/app/components/AppRouterProviders.tsx

@@ -11,6 +11,7 @@ import { ClientConfigProviderEffect } from '@/client-config/components/ClientCon
 import { MainContextStoreProvider } from '@/context-store/components/MainContextStoreProvider';
 import { ErrorMessageEffect } from '@/error-handler/components/ErrorMessageEffect';
 import { PromiseRejectionEffect } from '@/error-handler/components/PromiseRejectionEffect';
+import { HeadlessFrontComponentMountRoot } from '@/front-components/components/HeadlessFrontComponentMountRoot';
 import { ApolloCoreProvider } from '@/object-metadata/components/ApolloCoreProvider';
 import { ObjectMetadataItemsLoadEffect } from '@/object-metadata/components/ObjectMetadataItemsLoadEffect';
 import { ObjectMetadataItemsProvider } from '@/object-metadata/components/ObjectMetadataItemsProvider';
@@ -68,6 +69,7 @@ export const AppRouterProviders = () => {
                                     <PageFavicon />
                                     <Outlet />
                                     <GlobalFilePreviewModal />
+                                    <HeadlessFrontComponentMountRoot />
                                   </StrictMode>
                                 </DialogManager>
                               </DialogComponentInstanceContext.Provider>