fix(measurements): label DayDrillDown GET failure as load error not save error

The per-day drill-down used measurements.saveError in its fetch-error branch, which surfaced 'Fehler beim Speichern' on a read failure. Adds a measurements.loadError key in every locale and points the GET error path at it.

src/components/measurements/measurement-list.tsx

@@ -1055,7 +1055,7 @@ function DayDrillDown({
   if (error) {
     return (
       <div className="text-destructive py-2 text-xs">
-        {t("measurements.saveError")}
+        {t("measurements.loadError")}
       </div>
     );
   }