OPT-36: Leftover solar counts what Cheap hours and Solar first batteries will give before buying

Live 0.20.0: A (Leftover solar, 60 %) charged to 95 % while B (Cheap hours,
94 %) already covered the expensive hours. dayplan.plan() now takes off the
shortfall what Cheap hours batteries will hold when the hours start (the
ceiling or what their cheap run reaches under the peak aim) and what Solar
first batteries will still hold after the night's use. Home reads a give
block after the planned charge, plan_cover() is the plan's own figure, and
the Why line says other batteries cover.

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

goodwe_controller/app/ui_text/en.json

@@ -357,6 +357,7 @@
       "no_prices": "No prices, so it follows the house.",
       "no_spread": "Prices differ too little, so it follows the house.",
       "sun_fills": "Enough sun is forecast, so it does not charge from the grid.",
+      "others_cover": "Other batteries cover the expensive hours. It does not charge from the grid.",
       "tops_up": "It charges from the grid to {pct}. That covers {kwh} of expensive hours the sun will not.",
       "no_forecast": "No solar forecast, so it charges from solar only."
     },