Add mobile/desktop device detection and QR code functionality to VSCode extension

- Implement device detection to differentiate between mobile and desktop environments
- Desktop view: keep existing "Open Catnip Interface" button and add QR code for mobile access
- Mobile view: replace button with cat emoji logo linking to Catnip interface
- Add QR code generation using qrcode library for https://catnip.run?cs=$CODESPACE_NAME
- Include styled webview panel for QR code display with VSCode theming
- Update extension package with new command and dependencies

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: Claude