[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-server/src/engine/core-modules/application/utils/from-front-component-manifest-to-universal-flat-front-component.util.ts

@@ -20,6 +20,7 @@ export const fromFrontComponentManifestToUniversalFlatFrontComponent = ({
     builtComponentPath: frontComponentManifest.builtComponentPath,
     componentName: frontComponentManifest.componentName,
     builtComponentChecksum: frontComponentManifest.builtComponentChecksum,
+    isHeadless: frontComponentManifest.isHeadless ?? false,
     createdAt: now,
     updatedAt: now,
   };