app: move theme= from Blocks.launch() to Blocks() ctor (Gradio 5 API)

app.py

@@ -43,7 +43,7 @@ correct 3D model.
 - **Code**: [`huggingface/cadgenbench`](https://github.com/huggingface/cadgenbench).
 """
 
-with gr.Blocks(title="CADGenBench Leaderboard") as app:
+with gr.Blocks(title="CADGenBench Leaderboard", theme=gr.themes.Soft()) as app:
     gr.Markdown(
         "# CADGenBench Leaderboard\n"
         "_Benchmarking AI-driven CAD generation._"
@@ -108,4 +108,4 @@ to publish the resulting row on the public leaderboard.
 
 
 if __name__ == "__main__":
-    app.launch(theme=gr.themes.Soft())
+    app.launch()