[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/database/typeorm/core/migrations/common/1771509478665-add-is-headless-to-front-component.ts

@@ -0,0 +1,19 @@
+import { type MigrationInterface, type QueryRunner } from 'typeorm';
+
+export class AddIsHeadlessToFrontComponent1771509478665
+  implements MigrationInterface
+{
+  name = 'AddIsHeadlessToFrontComponent1771509478665';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."frontComponent" ADD "isHeadless" boolean NOT NULL DEFAULT false`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."frontComponent" DROP COLUMN "isHeadless"`,
+    );
+  }
+}