* fix(whisper): use bundled GPU libs and skip software Vulkan devices
AppImage 0.15.0 shipped a CPU-only pywhispercpp wheel, so the Settings
GPU picker and host vulkaninfo never moved inference off the CPU. Rebuild
pywhispercpp with Vulkan in the AppImage, log the libraries that actually
load, skip llvmpipe in auto-select, and document how to verify.
Fixes#604
* fix(appimage): pin gcc/g++ for Vulkan pywhispercpp rebuild
Hosts that default cc/c++ to clang fail CMAKE's C++ test because clang
does not search gcc's libstdc++ path. Default the rebuild to gcc/g++.
