feat: update app icon to new green MS logo

Replaced all AppIcon sizes (16x16 through 1024x1024) and AppIcon.icns
with the new green branding. All other in-app logos (AppLogo, BrandLogo,
MenuBarIcon) remain unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: MehmedHunjra