=LET(
  _data, $A$1:$B$14,
  _months, SEQUENCE($D$1,1,1,1),
  _dates, DATE(2025, _months, 1),
  _monthVals,
     MAP(
       _dates,
       LAMBDA(d,
         SUMIFS(
           INDEX(_data,,2),
           INDEX(_data,,1), d
         )
       )
     ),
  VSTACK(_dates, _monthVals)
)