GPU fixes

.env.example

@@ -54,6 +54,11 @@ WHISPER_CPU_THREADS=4
 # 4) Use GPU-friendly precision and device
 # WHISPER_DEVICE=cuda
 # WHISPER_PRECISION=float16
+# 5) (Build-time) use an NVIDIA CUDA runtime base image for the app containers.
+# Set an image tag that exists for your architecture (most CUDA images are amd64):
+# GPU_BASE_IMAGE=nvidia/cuda:11.8.0-cudnn8-runtime-ubuntu22.04
+#
+# If you are on ARM64 without discrete NVIDIA GPU, leave GPU_BASE_IMAGE unset and run CPU-only.
 
 # Docker volumes paths
 LIBRARY_HOST_DIR=/mnt/nfs/library