Remove unused Call Display features: Mobile Layout, Webcall Display URL, and QR Code

[coderabbitai]

Description

Remove unused features from the Call Display (Aufrufanzeige) system:

1. Layout mobile Aufrufanzeige - Mobile layout for call display
2. Webcall Display URL - Webcall display URL functionality
3. QR Code feature - QR code generation and printing

Reason

These features are not being used in the application and their removal would:

• Simplify the codebase
• Eliminate the dependency on react-to-print library (or at least reduce complexity of upgrading it)
• Reduce maintenance burden

Known Locations

• QR Code feature: zmsadmin/js/block/calldisplay/qrCode/index.js
• The QR code component uses react-to-print library for print functionality

Context

This issue was created as follow-up to PR #1614 which involves upgrading react-to-print to v3. Since these call display features are unused, removing them would be preferable to migrating the code to the new API.

Related PR: #1614
Requested by: @ThomasAFink
Comment: #1614