🚧(frontend) add applications menu PoC

Based on works from @manuhabitela, introduce a PoC of the future component.
ApplicationsMenu component is still under construction.

This code was committed for the Wednesday 26th demo, to showcase our future
works. This Next.js integration could be improved, and will for sure!
Don't blame me.

src/frontend/apps/e2e/__tests__/app-desk/header.spec.ts

@@ -27,7 +27,9 @@ test.describe('Header', () => {
       /Marianne/i,
     );
 
-    await expect(header.getByAltText('Cells icon')).toBeVisible();
+    await expect(
+      header.getByText('Les applications de La Suite numérique'),
+    ).toBeVisible();
 
     await expect(header.getByAltText('Language Icon')).toBeVisible();