fix: remove pre-download step, model downloads at runtime startup

Dockerfile

@@ -20,8 +20,5 @@ ENV HOME=/home/user \
 WORKDIR /home/user/app
 COPY --chown=user:user . .
 
-# Pre-download model during build (avoids slow cold start)
-RUN python3 -c "from transformers import AutoModel; AutoModel.from_pretrained('ShandaAI/FloodDiffusionTiny', trust_remote_code=True)"
-
 EXPOSE 7860
 CMD ["python3", "app.py", "--port", "7860"]