Fix numcodecs ARM64 compatibility in Dockerfile.spark

- Skip torch from requirements (already installed with CUDA)
- Upgrade numcodecs to >=0.13.0 (ARM64 compatible)

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

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

docker/Dockerfile.spark

@@ -19,9 +19,11 @@ RUN pip3 install --no-cache-dir \
     torch \
     --index-url https://download.pytorch.org/whl/cu124
 
-# Copy and install remaining Python requirements
+# Copy requirements and install (excluding torch since we installed it above)
 COPY requirements.txt .
-RUN pip3 install --no-cache-dir -r requirements.txt
+RUN grep -v "^torch==" requirements.txt > requirements-spark.txt && \
+    sed -i 's/numcodecs==0.11.0/numcodecs>=0.13.0/' requirements-spark.txt && \
+    pip3 install --no-cache-dir -r requirements-spark.txt
 
 # Copy backend code
 COPY backend/ ./backend/