Fix Dockerfile.spark for ARM64 architecture (DGX Spark)

- Use NVIDIA NGC pytorch image (nvcr.io/nvidia/pytorch:24.01-py3)
- Supports ARM64/aarch64 with CUDA

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker/Dockerfile.spark

@@ -1,11 +1,10 @@
-# GPU-enabled Dockerfile for DGX Spark deployment
-FROM pytorch/pytorch:2.1.0-cuda12.1-cudnn8-runtime
+# GPU-enabled Dockerfile for DGX Spark deployment (ARM64/aarch64)
+# Using NVIDIA NGC PyTorch image which supports ARM64
+FROM nvcr.io/nvidia/pytorch:24.01-py3
 
-# Install system dependencies
+# Install additional system dependencies
 RUN apt-get update && apt-get install -y \
     curl \
-    build-essential \
-    git \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app