fix: ensure to_native is at the very top of app.py and always in scope

dashboard/app.py

@@ -5,6 +5,29 @@ Mangrove ER Model Dashboard
 - To add a new model, add its config to configs/ and add an entry to MODEL_CONFIGS below.
 - Each tab shows the results for the base config (no parameter editing).
 """
+   def to_native(obj):
+       import numpy as np
+       import pandas as pd
+       if isinstance(obj, pd.DataFrame):
+           obj = obj.applymap(lambda x: to_native(x))
+           obj.index = obj.index.map(to_native)
+           obj.columns = obj.columns.map(to_native)
+           return obj
+       elif isinstance(obj, pd.Series):
+           obj = obj.map(to_native)
+           obj.index = obj.index.map(to_native)
+           return obj
+       elif isinstance(obj, dict):
+           return {to_native(k): to_native(v) for k, v in obj.items()}
+       elif isinstance(obj, list):
+           return [to_native(x) for x in obj]
+       elif isinstance(obj, tuple):
+           return tuple(to_native(x) for x in obj)
+       elif isinstance(obj, (np.generic, np.ndarray)):
+           return obj.item() if obj.size == 1 else obj.tolist()
+       else:
+           return obj
+
 import gradio as gr
 from pathlib import Path
 from src.er_model import ERModel