Update Dockerfile

Dockerfile

@@ -14,5 +14,8 @@ WORKDIR /
 # Install requirements.txt 
 RUN pip install --no-cache-dir --upgrade -r backend/requirements.txt
 
+# Change to backend directory
+WORKDIR "/backend"
+
 # Start the FastAPI app on port 7860, the default port expected by Spaces
 CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "7860"]