chore(docker): bind uvicorn to platform PORT (fallback 7860) for HF routing

Dockerfile

@@ -116,5 +116,5 @@ ENV PYTHONUNBUFFERED=1
 # Expose port 7860 (required for Hugging Face Spaces)
 EXPOSE 7860
 
-# Run the API server on port 7860 (HF Spaces requirement)
-CMD ["python", "-m", "uvicorn", "api_server:app", "--host", "0.0.0.0", "--port", "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}"]