* fix(whisper): use CUDA device 0 when pywhispercpp is CUDA-backed
Vulkan GPU enumeration on hybrid laptops lists the iGPU as GPU0 and the
dGPU as GPU1, but CUDA ordinals always place the first NVIDIA GPU at 0.
Auto mode and the settings UI were passing Vulkan indices into CUDA
pywhispercpp, which silently fell back to CPU inference.
Detect the actual pywhispercpp backend before selecting gpu_device and
map CUDA installs to device 0. Vulkan-backed installs keep Vulkan indices.
* test(whisper): cover CUDA gpu_device selection branches for codecov
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Co-authored-by: Jatin K Malik <jatinkrmalik@gmail.com>
