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/messages.py

@@ -906,6 +906,8 @@ HINTS = {
     "trade_charge": "Trading: charging while the price is low",
     "trade_give": "Trading: giving power while the price is high",
     "trade_off": "Trading: waiting for a better price",
+    "forecast_read": "Solar forecast read, the day plan uses it",
+    "forecast_none": "No solar forecast, so Leftover solar takes solar only",
     "split": "The power split between inverters changed",
     "clash": "Two limits clash, inverters set to 0 W",
     "no_setpoint": "An inverter has no “Setpoint entity”, inverters stay at 0 W",
@@ -1172,6 +1174,9 @@ LABELS = {
     "batt_entity": "Battery power entity",
     "pv_entity": "Solar production entity",
     "pv_entities": "Solar production entities, per inverter",
+    "pv_forecast_entity": "Solar forecast, today",
+    "pv_forecast_tomorrow_entity": "Solar forecast, tomorrow",
+    "solar_trust_pct": "Trust in the forecast",
     "p1_phase_import_entities": "Import entities per phase",
     "p1_phase_export_entities": "Export entities per phase",
 }