fix: 修正融合出现的问题

internal/fusion/fusion.go

@@ -509,15 +509,15 @@ func resolveIssuedAtInBucket(db *sql.DB, stationID, provider string, bucketHour
 func loadForecastSamples(db *sql.DB, stationID, provider string, issued time.Time) ([]forecastSample, error) {
 	const q = `
         SELECT forecast_time,
-               rain_mm_x1000,
-               temp_c_x100,
-               humidity_pct,
-               wind_speed_ms_x1000,
-               wind_gust_ms_x1000,
-               wind_dir_deg,
-               precip_prob_pct,
-               pressure_hpa_x100,
-               uv_index
+               COALESCE(rain_mm_x1000, 0),
+               COALESCE(temp_c_x100, 0),
+               COALESCE(humidity_pct, 0),
+               COALESCE(wind_speed_ms_x1000, 0),
+               COALESCE(wind_gust_ms_x1000, 0),
+               COALESCE(wind_dir_deg, 0),
+               COALESCE(precip_prob_pct, 0),
+               COALESCE(pressure_hpa_x100, 0),
+               COALESCE(uv_index, 0)
         FROM forecast_hourly
         WHERE station_id=$1 AND provider=$2 AND issued_at=$3
         ORDER BY forecast_time ASC`