Fix st.dataframe width parameter (use_container_width)

st.dataframe() uses use_container_width=True, not width="stretch"
(width="stretch" is for st.plotly_chart only)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app.py

@@ -443,7 +443,7 @@ if has_materials and has_labor and has_overhead:
                 "Total Cost": "€{:.2f}",
                 "Recycled %": "{:.0f}%",
             }),
-            width="stretch",
+            use_container_width=True,
             hide_index=True,
         )
 
@@ -645,7 +645,7 @@ summary_df = pd.DataFrame({
     ],
 })
 
-st.dataframe(summary_df, width="stretch", hide_index=True)
+st.dataframe(summary_df, use_container_width=True, hide_index=True)
 
 # Highlight the key insight
 profit_advantage = circular_cum_profit - linear_cum_profit
@@ -1231,7 +1231,7 @@ with st.expander("Full Scale Comparison Table"):
             "Products Saved": "{:,}",
             "CO2 Saved": "{:,.0f} kg",
         }),
-        width="stretch",
+        use_container_width=True,
         hide_index=True,
     )