feat(attendance): add SetCountsAsync to set all three age groups for a date

API/ROLAC.API/Services/IMealAttendanceService.cs

@@ -22,6 +22,13 @@ public interface IMealAttendanceService
     /// </summary>
     Task<AttendanceCountsDto> SetAsync(DateOnly date, string category, int value);
 
+    /// <summary>
+    /// Overwrites all three age-group columns for <paramref name="date"/> with absolute
+    /// values (each clamped at zero), creating the row if it does not exist, and returns
+    /// the resulting authoritative counts. Used by the back-office Sunday-attendance editor.
+    /// </summary>
+    Task<AttendanceCountsDto> SetCountsAsync(DateOnly date, int adult, int youth, int kid);
+
     /// <summary>Returns the daily counts within the inclusive date range, ordered by date (for the dashboard).</summary>
     Task<IReadOnlyList<AttendanceCountsDto>> GetRangeAsync(DateOnly from, DateOnly to);
 }