App switcher (gaufre) and user menu updates

[robin-lecomte]

• Move the app settings button into the user menu
• Remove color gradients in both windows
• Add scrolling and remove the “See more” button in the app switcher
• Align horizontal sizing across both windows
• Remove mobile-specific versions to (1) reduce exceptions and (2) keep the user in context without full-screen display

Linked to the bottom menu and settings update issue: #277

FIGMA : User Menu - App Swicher