[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/metadata-modules/flat-front-component/constants/flat-front-component-editable-properties.constant.ts

@@ -7,4 +7,5 @@ export const FLAT_FRONT_COMPONENT_EDITABLE_PROPERTIES = [
   'sourceComponentPath',
   'builtComponentPath',
   'componentName',
+  'isHeadless',
 ] as const satisfies MetadataEntityPropertyName<'frontComponent'>[];

packages/twenty-server/src/engine/metadata-modules/flat-front-component/utils/from-create-front-component-input-to-flat-front-component-to-create.util.ts

@@ -33,6 +33,7 @@ export const fromCreateFrontComponentInputToFlatFrontComponentToCreate = ({
     builtComponentPath: createFrontComponentInput.builtComponentPath,
     componentName: createFrontComponentInput.componentName,
     builtComponentChecksum: createFrontComponentInput.builtComponentChecksum,
+    isHeadless: false,
     workspaceId,
     createdAt: now,
     updatedAt: now,

packages/twenty-server/src/engine/metadata-modules/flat-front-component/utils/from-flat-front-component-to-front-component-dto.util.ts

@@ -20,6 +20,7 @@ export const fromFlatFrontComponentToFrontComponentDto = (
     : undefined,
   workspaceId: flatFrontComponent.workspaceId,
   applicationId: flatFrontComponent.applicationId,
+  isHeadless: flatFrontComponent.isHeadless,
   createdAt: new Date(flatFrontComponent.createdAt),
   updatedAt: new Date(flatFrontComponent.updatedAt),
 });

packages/twenty-server/src/engine/metadata-modules/flat-front-component/utils/from-front-component-entity-to-flat-front-component.util.ts

@@ -31,6 +31,7 @@ export const fromFrontComponentEntityToFlatFrontComponent = ({
     builtComponentPath: frontComponentEntity.builtComponentPath,
     componentName: frontComponentEntity.componentName,
     builtComponentChecksum: frontComponentEntity.builtComponentChecksum,
+    isHeadless: frontComponentEntity.isHeadless,
     workspaceId: frontComponentEntity.workspaceId,
     universalIdentifier: frontComponentEntity.universalIdentifier,
     applicationId: frontComponentEntity.applicationId,