feat: Update Solar Demo site to use 400W panel defaults.

Solar API is moving to 400W panels as default; this change aligns with a change
in default panel sizing, so making the default on the demo site match the API
output will generate more reasonable behavior.

Author: crschmidt

src/routes/sections/Sections.svelte

@@ -36,7 +36,7 @@
 
   // User settings
   let monthlyAverageEnergyBillInput = 300;
-  let panelCapacityWattsInput = 250;
+  let panelCapacityWattsInput = 400;
   let energyCostPerKwhInput = 0.31;
   let dcToAcDerateInput = 0.85;