fix: move LoginButton to top-level Blocks for OAuth redirect to work

app.py

@@ -322,6 +322,14 @@ def build_app() -> gr.Blocks:
 
         gr.Markdown(HEADER_MD)
 
+        # HF OAuth login — must be at top level of Blocks for the redirect to work
+        with gr.Row():
+            gr.LoginButton(scale=0)
+            gr.Markdown(
+                "_Sign in with your HuggingFace account so we can credit your contribution._",
+                scale=1,
+            )
+
         with gr.Row():
             # ---- Left column: config + exercise ----
             with gr.Column(scale=1):
@@ -384,9 +392,6 @@ def build_app() -> gr.Blocks:
                 gr.Markdown("---")
                 gr.Markdown("### Submit your solution")
 
-                with gr.Row():
-                    gr.LoginButton()
-
                 time_slider = gr.Slider(
                     label="Time spent (minutes)",
                     minimum=1,