fix: proper VRAM cleanup on model unload + CUDA alloc config

- Force gc.collect() before torch.cuda.empty_cache() to ensure all
  model references are released
- Set PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True in container

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kischdle/llmux/Dockerfile

@@ -57,6 +57,9 @@ COPY --from=builder /usr/local/lib/python3.12/dist-packages/llama_cpp_python* /u
 COPY llmux/ /app/llmux/
 WORKDIR /app
 
+# Avoid CUDA memory fragmentation when swapping models
+ENV PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True
+
 # Run the server
 EXPOSE 8081
 CMD ["uvicorn", "llmux.main:app", "--host", "0.0.0.0", "--port", "8081"]