The ptrkrysik/gr-gsm repo uses SWIG which is incompatible with
GNU Radio 3.10+. The bkerler fork supports modern GNU Radio and
builds successfully on current Ubuntu/Debian systems.
Updated all references in Dockerfile, setup.sh, dependencies.py,
and error messages.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>