Fix: Use issued_at instead of target_at for zero-hour resolved truth timestamps

The zero-hour forecasts (observations) were being saved with resolved_at = target_at,
which could be in the future. This caused them to be filtered out by the time-based
query in load_display_dataset(). Now using issued_at (when the observation was made)
ensures the timestamps fall within the valid display range.

gibil/classes/weather_store.py

@@ -183,7 +183,7 @@ class WeatherStore:
     ) -> int:
         truth_points = [
             WeatherResolvedTruth(
-                resolved_at=point.target_at,
+                resolved_at=point.issued_at,
                 source="open_meteo_zero_hour",
                 temperature_c=point.temperature_c,
                 shortwave_radiation_w_m2=point.shortwave_radiation_w_m2,
@@ -237,7 +237,7 @@ class WeatherStore:
                     ORDER BY resolved_at
                     LIMIT 5000
                     """,
-                    (start_at, end_at),
+                    (start_at, now),
                 )
                 truth_rows = cursor.fetchall()