Fix HuggingFace Spaces compatibility: use Gradio 4.44.0

- Revert to Gradio 4.44.0 for HF Spaces compatibility
- Update to Gradio 4.x API (show_download_button instead of buttons)
- Move theme back to Blocks() constructor for Gradio 4.x
- Keep 3D viewer fixes (MutationObserver, proper positioning)

Fixes ImportError with huggingface_hub on HF Spaces.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app.py

@@ -142,6 +142,7 @@ example_smiles = [
 
 with gr.Blocks(
     title="Drug-Likeness Predictor",
+    theme=gr.themes.Soft(),
     head='''
     <script src="https://3Dmol.org/build/3Dmol-min.js"></script>
     <script>
@@ -212,7 +213,7 @@ with gr.Blocks(
             image_output = gr.Image(
                 label="2D Molecular Structure",
                 type="pil",
-                buttons=["download", "fullscreen"],
+                show_download_button=True,
             )
 
     viewer_html = gr.HTML(label="3D Interactive Viewer")
@@ -235,4 +236,4 @@ with gr.Blocks(
     )
 
 if __name__ == "__main__":
-    demo.launch(theme=gr.themes.Soft())
+    demo.launch()

requirements.txt

@@ -1,5 +1,5 @@
 tensorflow==2.15.0
-gradio>=6.0.0
+gradio==4.44.0
 rdkit-pypi>=2022.9.5
 joblib>=1.3.2
 numpy<2.0.0