OPT-11 P4: solar forecast and day plan

A Home Assistant solar forecast (Forecast.Solar, Solcast or Open-Meteo
shapes) and the add-on's own hourly house use decide, before each cheap
run, whether the sun will fill each battery before the expensive hours.
Leftover solar then buys from the grid only the shortfall; Cheap hours only
skips the part the sun covers; Solar first never grid-charges. No, stale or
failed forecast: P3 option A exactly (12 digests pinned from 5a4cdc2).

Replay (16 recorded days, forecast errors from Elia's day-ahead BE solar):
year-earlier prices P4 19.15 vs P2 19.33 / option A 19.44 / old trade 18.14;
real 2026 prices P4 29.19 vs 32.26 / 32.01 / 31.40 EUR net.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/app/uilayout.py

@@ -129,7 +129,14 @@ GROUPS = (
                              wizard=3),)),
         # OPT-11: the switch that turns battery modes on. Each battery's mode
         # and on/off switch are runtime state on the Batteries screen.
-        Part("modes", (Field("battery_modes_enabled", TOGGLE),)),
+        Part("modes", (
+            Field("battery_modes_enabled", TOGGLE),
+            # OPT-11 P4: the solar forecast; today's also on Settings, Simple.
+            Field("pv_forecast_entity", ENTITY, kind="energy", simple=True,
+                  note="forecast"),
+            Field("pv_forecast_tomorrow_entity", ENTITY, kind="energy"),
+            Field("solar_trust_pct", SLIDER, "%", step=5),
+        )),
     )),
     Group("tariff", (
         Part("", (