* feat: detect incompatible Intel GPUs and fallback to CPU
Implements two-layer protection for users with older Intel GPUs that lack
VK_KHR_16bit_storage support required by whisper.cpp Vulkan backend.
Affected GPUs: Intel Gen7 and older (Ivy Bridge, Haswell, Sandy Bridge)
- Intel HD Graphics 2500/4000 (Ivy Bridge)
- Intel HD Graphics 4400/4600 (Haswell)
Layer 1: Install-Time Detection (Prevention)
- New check_vulkan_gpu_compatibility() function in install.sh
- Parses GPU name from vulkaninfo output
- Checks against known incompatible patterns
- Shows clear warning and recommends CPU backend
- Updates detect_whispercpp_backends() to skip Vulkan for incompatible GPUs
Layer 2: Runtime Fallback (Safety Net)
- Added error handling in recognition_manager.py _init_whispercpp()
- Catches RuntimeError with "16-bit storage" or "Unsupported device"
- Automatically disables Vulkan/CUDA and retries with CPU
- Shows desktop notification explaining the fallback
Fixes#238
* fix(gpu): improve compatibility detection and add tests
