fix: Gradio 5 compatibility — remove height param, allow custom dropdown values

- gr.Dataframe no longer accepts 'height', use 'max_height' instead
- gr.Dropdown requires allow_custom_value=True for dynamic values
- Removed row_count parameter (not supported in Gradio 5)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -342,9 +342,8 @@ def init_leaderboard(dataframe, visible_columns=None):
         datatype=datatypes,
         interactive=False,
         wrap=True,
-        height=2500,
+        max_height=2500,
         elem_id="leaderboard-table",
-        row_count=len(display_df),
     )
 
 
@@ -754,6 +753,7 @@ with demo:
                         label="Columns",
                         multiselect=True,
                         value=get_initial_columns(),
+                        allow_custom_value=True,
                         interactive=True,
                         visible=False,
                         scale=1,