Fix dashboard imports for Streamlit multi-page routing

- Add sys.path.insert at top of app.py and all 5 page files
- Fix .streamlit/config.toml CORS/XSRF conflict
- Remove duplicate st.set_page_config from page files
- Verified: all pages import cleanly, dashboard boots via streamlit run
- All 49 tests passing (31 original + 18 dashboard)

dashboard/pages/05_lab.py

@@ -1,3 +1,4 @@
+import sys; from pathlib import Path; _p = Path(__file__).resolve().parent.parent.parent; str(_p) not in sys.path and sys.path.insert(0, str(_p))
 """Page 5 — Model Lab.
 
 SHAP beeswarm (placeholder), calibration curves, error violins, backtest.
@@ -112,7 +113,6 @@ def _feature_importance_plot(players):
 
 
 def run():
-    st.set_page_config(page_title="Model Lab — Fantabeto", page_icon="🧪", layout="wide")
     inject_css()
     votes, preds, metrics, players = _get_data()