Add missing neutral_hue parameter to match SR theme exactly

SR app uses theme=gr.themes.Default(primary_hue="blue", neutral_hue="gray")
while our demos only used theme=gr.themes.Default().

The neutral_hue="gray" parameter may be critical for consistent background rendering on HuggingFace Spaces.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

app.py

@@ -136,7 +136,7 @@ def load_example_image(example_path):
 
 # Create Gradio interface
 with gr.Blocks(
-    theme=gr.themes.Default(),
+    theme=gr.themes.Default(primary_hue="blue", neutral_hue="gray"),
     title="MobileNetV2 Classification",
     css="""
     body {