fix(docker): use /bin/sh -lc so expands for uvicorn

Dockerfile

@@ -116,5 +116,5 @@ ENV PYTHONUNBUFFERED=1
 # Expose port 7860 (required for Hugging Face Spaces)
 EXPOSE 7860
 
-# Run the API server using the platform PORT (fallback to 7860)
-CMD ["python", "-m", "uvicorn", "api_server:app", "--host", "0.0.0.0", "--port", "${PORT:-7860}"]
+# Run via shell so ${PORT} expands (fallback to 7860)
+CMD ["/bin/sh", "-lc", "python -m uvicorn api_server:app --host 0.0.0.0 --port ${PORT:-7860}"]