feat(fe): KsDataGrid - Enter key acts like Tab (column-only navigation)

Changed Enter key behavior to move only to next editable column within same row
(no row change, just like Tab key).

Previous: Enter → next column OR next row (if last column)
New: Enter → next column only (last column does nothing)

This makes data entry more predictable and consistent with Tab behavior.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/shared/ui/components/KsDataGrid.vue

@@ -215,19 +215,8 @@ function navigateToNextCell(params: NavigateToNextCellParams): CellPosition | nu
           column: nextCol,
           rowPinned: previousCell.rowPinned
         }
-      } else {
-        const nextRowIndex = previousCell.rowIndex + 1
-        const firstCol = editableCols[0]
-        const colId = firstCol.getColId()
-        setTimeout(() => {
-          params.api.startEditingCell({ rowIndex: nextRowIndex, colKey: colId })
-        }, 30)
-        return {
-          rowIndex: nextRowIndex,
-          column: firstCol,
-          rowPinned: previousCell.rowPinned
-        }
       }
+      return null
     }
   }