feat: Improve kebab menu for mobile devices

[Aryan-Verma-999]

Description

On mobile viewports (375px and below), clicking the kebab menu (⋮) in the EmbeddedChat header opens a dropdown that is not optimized for mobile responsiveness.
Currently, it uses the same UI as the desktop version, which results in:

• Very small touch targets
• Poor spacing
• Difficult interaction on smaller screens
  As shown in the screenshot, the menu is compact and not user-friendly on mobile devices.

Steps to Reproduce

1. Open EmbeddedChat in Chrome DevTools with a mobile device preset (iPhone SE, 375px)
2. Click the ⋮ kebab menu in the top-right header
3. Observe the dropdown menu

Screenshots

[KshitijShukla30]

Hi @Aryan-Verma-999 @Spiral-Memory,
I would like to work on this issue. Could you please assign it to me?